R390 Road Car '97 (won at GTAS Laguna) at Tahiti, no hp upgrades, everything else fair game. Results so far:
FujiK: 57.234
Pupik: 57.955
MidasGT: 57.997
The_Masaru05: 58.002
Kurtis: 58.687
milefile: 58.799
First thing to note, this engine is designed to accept a lot more power, so stock, the peak hp comes well before the redline, and so it will be much more effective in the hands of a competent MT driver. I had to set the gears to only use 5 out of the 6 available in order to get the RPM's to drop low enough on shift up to catch the peak power, and still have to suffer through the sharp drop in power in the last 1000rpms before the AT shifts up again.
59.166 on lap 15 I thought was pretty good for this setup, and I can see myself getting down to the mid 58's, but I'm 100% positive you need to drive MT and use all six gears tightly around the peak power to get into the low 57's.
Edit: oops, I did this with the R390 Road Car '98 instead of the '97, I'll have to try again since the '98 sits at 2.92 kg/hp and the '97 is a little less powerful but much lighter and so achieves a 10% better weight to power ratio of 2.62 kg/hp.
Edit: 58.609 with the '97 R390 Road Car on like lap 12... again could do better, maybe down to 58 given 50 laps with breaks.