Okay, I've pretty well hashed out all the non-racing-only Skylines, and here's the results.
There are surprisingly a lot of variables involved. Let's consider them.
1) Stock rideheight. This determines your ultimate minimum rideheight, and so center of gravity, and will affect your handling. Here's how the cars compare:
105mm - both NISMO 400R's and the R33 LM Road car
130mm - all Tommykaira's and the R34 GT-R V-Spec
135mm - all Mine's, '89 and '91 R32 GT-R's, and Prince 280MR
140mm - R31 GTS-R, R32 NISMO, V-Spec and V-Spec II, and R34 25GT-Turbo
145mm - R32 GTS-T Type M and GTS25 Type S, R33 GT-R '95, '97 and 4 Doors and R33 GTS25T Type M, and R34 GT-R
150mm - R32 GTS4 and R33 GT-R 4 Door NISMO
155mm - R30 RSX-2000
160mm - KPGC10
So, 400R's and the LM Road car are going to rule on this stat. Tommykaira's are looking pretty good, and the R34 GT-R V-Spec has a leg up on the base R34 GT-R.
2) Stock Spings. Of course this is unimportant if you're adding Pro suspension, but if you just want to go stock, sport, or semi-race, this is useful information.
Mine's are the best by far, of course, with 400R's a little behind. Then we have the R33 and R34 Tommykaira's, and together with them only a little behind the R34 GT-R V-Spec, the R33 4 Door NISMO, and the R33 LM Road Car. Following in order after that: the Prince 280MR, the other two Tommykairas, the R33 GT-R's, the R34 GT-R, the R33 GT-R 4 Door, the R34 GT-Turbo, the R33 GTS25T, the R32 GT-R '89, the KPGC10, the R32 GT-R '91, the R32 NISMO and both V-Specs, the two R32 FR's, the R31. the R30, and finally the R32 GTS4
3) Stock Downforce. Sum front and rear and you get the following totals:
45 - the NISMO 400R's - unusually high, 20F and 25R
40 - R32.5 and R34 Mine's, R33 and R34 Tommykaira's, and all R32, R33, and R34 GT-R's
36 - a funny number, 15F and 21R, R31 and R32 Tommykaira's, R34 GT25-Turbo, and R31 and R30
33 - the rest, including notably the R33 Mine's, the R33 LM Road Car, and the Prince 280MR
4) Drag coefficient. R32's have 0.40, R33's have 0.35, and R34's have 0.37. So, R33's are the best at cutting through wind resistance at high speed, and R32's are pigs. There are a few exceptions, however. The R33 LM Road Car appears to have a drag of 0.40. Both R32 FR's appear to have drag of 0.37. The R32 Tommykaira appears to have a drag of 0.35, as do both R31's, the R30, and the KPGC10.
5) Tire Size, from worst to best, stock
185/60 R13 - KPGC10
185/55 R16 - R30 RSX-Turbo
205/55 R15 - R31 Tommykaira
205/50 R16 - Both FR R32's, R32 Tommykaira, R31 GTS-R, and R33 GTS25T
205/45 R17 - '89 and '91 R32 GT-R's, R32 GTS4, and R34 25GT-Turbo
225/45 R17 - all Mine's, R32 NISMO, R32 GT-R V-Spec II, both 400R's, all R33 GT-R's including 4 Doors, Prince 280MR, and Tommykaira
225/40 R18 - R34 GT-R and GT-R V-Spec
245/45 R19 - R33 LM Road Car
245/30 R19 - Tommykaira R34 (amazing, but to be honest I'm not sure I'm right about this one, though it's definitely either 18" or 19")
6) Engine Displacement. The R31 and R32 Tommykaira's are both basically 3L. the 400R's and the Prince 280MR are 2.8L. The GT-R's are all 2.6L, as is the R32 GTS25 Type S. The R33 and R34 FR's are 2.5L. The KPGC10, R30, R31, R32 GTS4, and R32 GTS-T Type M are all 2L.
7) Stock engine powerband quality. Complicated formula I've developed which includes consideration of number of gears, redline RPMs, peak power RPMs, and 75% of peak power RPMs.
R34 Tommykaira best by far, great flat spot for 1000rpms on top
R32 GT-R's next
R34 GT-R's close behind
R33 LM Road Car
R33 GTS25T Type M
R31 Tommykaira
Prince 280MR
R33 GT-R 4 Door
R33 Tommykaira, GT-R '95, and R34 25GT-turbo
R32 GTS25 Type S
Mine's R34
R32 GTS4 and GTS-T Type M, and R30
R33 4 Door NISMO
400R Preceiding
Mine's R33
KPGC10 and Mine's R32.5
R32 Tommykaira
R31 GTS-R
400R
8) Fully tuned powerband quality:
R33 LM Road Car
R32 GTS25 Type S
R34 GT-R's
400R Preceiding
R31 Tommykaira
R32 GTS4 and GTS-T Type M
R34 Tommykaira, R33 GT-R '95, and Mine's R34
R33 4 Door NISMO
R32 GT-R's and 400R
Mine's R32.5
Mine's R33
R33 GTS25T Type M and Prince 280MR
R33 4 Door
R33 Tommykaira
R34 25GT-Turbo
R30
R31 GTS-R
R32 Tommykaira - appallingly rotten
KPGC10
9) Stock weight to power, in kg/hp:
2.43 - Mine's R32.5
2.49 - Mine's R33 and R34
3.72 - R33 Tommykaira
3.94 - 400R's
4.22 - R34 Tommykaira
4.71 - R32 Tommykaira
4.77 - R34 GT-R
4.78 - Prince 280MR
4.83 - R34 GT-R V-Spec
4.85 - R32 GT-R '89
4.95 - R33 GT-R's
4.98 - R33 GT-R V-Spec's
5.02 - R32 GT-R '91
5.08 - R32 GT-R NISMO
5.16 - R33 LM Road Car
5.22 - R34 25GT-Turbo
5.64 - R33 GTS25T Type M
5.71 - R31 Tommykaira
5.97 - R32 GTS-T Type M
6.44 - R31 GTS-R
6.73 - R32 GTS4
6.79 - R30 RS-X 2000 Turbo
6.81 - R32 GTS25 Type S
7.01 - KPGC10
10) Fully tuned weight to power, before race mod
1.77 - R34 GT-R
1.78 - R32 Tommykaira
1.79 - R34 GT-R V-Spec
1.94 - R33 4 Door
1.97 - Mine's R32.5
2.00 - R32 GT-R '89
2.01 - Mine's R34 and R33
2.02 - R33 GT-R '95
2.04 - R33 LM Road Car
2.06 - R34 Tommykaira
2.08 - R33 Tommykaira
2.10 - R32 NISMO and V-Spec
2.15 - 400R's
2.18 - R33 4 Door NISMO
2.26 - Prince 280MR
2.67 - R34 25GT-Turbo
2.70 - R30
2.79 - R33 GTS25T Type M
2.83 - R31
2.93 - R32 GTS-T Type M
2.99 - KPGC10
3.07 - R31 Tommykaira
3.29 - R32 GTS4
3.53 - R32 GTS25 Type S
11) Tuned turbo lag. Many of the cars that end up getting 600+ hp will also get nasty turbo lag. A few will not, however. Best high power cars (least lag): R34 GT-R's, R32 Tommykaira, all Mine's, R33 LM Road Car. Worst cars for lag: R32 GT-R's, R33 Tommykaira and 4 Door (not NISMO), Prince 280MR, R32 GTS4
Now, what does all this mean in terms of performance? Here's the top fully tuned 400m times:
1) 9.572 - R34 GT-R V-Spec
2) 9.649 - R34 GT-R
3) 9.940 - R33 GT-R '95
4) 10.015 - Mine's R32.5
5) 10.143 - R33 4 Door NISMO
6) 10.174 - 400R
7) 10.177 - R32 GT-R V-Spec
8) 10.189 - Mine's R34
9) 10.257 - 400R Preceiding
10) 10.308 - R32 GT-R '89
11) 10.310 - R32 NISMO
12) 10.339 - R34 Tommykaira, and the rest fall off quickly after that
When looking at 1000m times the story is much the same, though the 400R Preceiding did much better than expected and was the 5th quickest from 400m to 1000m.
So, how about on the track? I went for best laps at SSR5 and Red Rock, and here's what I got, fully tuned:
R34 GT-R V-Spec fastest with a combined time of 2:25.384
+0.363 - R34 GT-R
+1.815 - Mine's R32.5
+2.274 - R33 GT-R '95
+2.355 - R32 Tommykaira
+2.605 - Mine's R34
+2.644 - 400R
+2.855 - R34 Tommykaira
+3.053 - 400R Preceiding
+3.246 - R32 GT-R V-Spec
+3.471 - R32 GT-R '89
+3.610 - R32 NISMO
+3.720 - R33 LM Road Car
+3.923 - R33 4 Door NISMO
+5.539 - R33 Tommykaira
+7.214 - R34 25GT-Turbo
+7.409 - Prince 280MR
+7.830 - R33 GTS25T Type M
+8.819 - R30 RS-X 2000
+9.576 - R32 GTS-T Type M
+10.755 - R31 GTS-R
+13.757 - R32 GTS25 Type S
+14.732 - R32 GTS4
That's the measurable stuff. Yeah, I left a few out of full testing. R33 GT-R 4 door is rubbish, use the NISMO instead. Mine's R33 is like the R34 but with one less gear, use the R34. Tommykaira R31 would fall just above the R30 RS-X, not sure why I didn't finish testing that one at Red Rock. KPGC10 2nd to last, right above R32 GTS4.
Out of all these Skylines, the ones I would recommend trying as most interesting/best in class are:
R34 GT-R V-Spec - sitting lower than the standard R34 does make a difference, enough to overcome the little bit of extra weight
Mine's R32.5 - surprisingly the fastest Mine's
R33 GT-R '95 - all other R33 GT-R's have an engine glitch. try this one and compare it to the R34 and R32 and see if you can notice that it has less drag
R32 Tommykaira - engine looks like rubbish, but there's so much of it it's okay. fastest FR Skyline, fun!
NISMO 400R - despite my predictions that the Preceiding model would be faster due to redline irregularity, this one came out on top in my testing. Try it to see what scraping your bottom on the ground feels like, lowest Skyline of them all. Definitely was the biggest over-achiever in terms of expected performance given tuned weight to power ratio. Most downforce helps it, too.
R34 Tommykaira - try it and let me know if you think it has great tires. in profile they look huge, but does it give better grip?
R32 GT-R, GT-R V-Spec, and NISMO - these three cars are very similar except for weight and tires and rideheight, fun to see if you can notice a difference
R33 LM Road Car - didn't perform as well as I wanted it to, but it was so different to drive I highly recommend it. Very wide and long, and huge tires. Power slides even when near stock, chuck-able. Definitely try it out.
R32 GTS25 Type S - only because it's the lone Skyline to get NA tuning
I could go on for a while longer, but I'll leave it at that and open the room for questions. And someday soon get back to the race cars and compare race modded Skylines.