Tried the '05 Pescarolo and won with it. Three stops - one every two laps (it might make three, but didn't want to push my luck) - and won by 39 seconds. It's every bit as fast as the Peugeot 908, but more squirrelly. If anything, it might be faster than the 908 - it's still pulling strong at 230mph without drafting. On braking and turn-in, though, it can be a handful.
If you can build up a 35-45 second lead with any of these cars, you should be cake for the win. Try to short-fill your gas on the pits to cut the pit time down. A full tank won't really get you three full laps, so no real sense in filling all the way up. 55-65 liters gets me a couple laps with a cushion, and 35 liters was more than enough to get me the last (seventh) lap when I came in at the end of lap 6 with a bit under a minute still on the clock in the race, and 53 seconds worth of lead over second place.
Now to figure out which car to try next... perhaps the 2J beckons...
Oh, and if you get yourself any of the "base" model LMP cars, you can paint them your favorite colors, so that's kind of nice. I have a sweet yellow and black 908.
* Edit: The Pesky was tuned with the big turbo. The mid turbo adds more torque, but I like the big one for more high-end power. One thing these cars *don't* need is more torque to fry the tires through 2nd, 3rd, and 4th gears! I like running above 200mph as much of the course as possible, and the big turbo makes that a snap.
** Edit # 2: The 2J wins. It will easily go 3 laps between pit stops. The downside? Since I was stopping every three laps, so were the other cars. When I do a stop every two laps in the other cars, so do the AI opponents. They seem to be keying on my stops. The upside? Doesn't matter - I still won by 38 seconds.
I'd say go with Racing Softs for the first stint (I used hards, and I was running low on fuel with practically no tire wear showing after that stint), then switch to Hards. By the end of the second stint, my hards were getting a bit tatty. You can go back to softs for the final lap, and splash in 30 liters of fuel.