Ford GTE and GT Spec II gr. 3's both work great. The Radical and BAC cars can both do it pretty handily. I'm trying the GT Mark IV next assuming I can get it down to 700pp. Any car that is under 2625lb with around 375-400hp can do it, the lower the weight and better fuel economy the better. Best bet as far as strategy is to run it at full fuel sip for the first half of lap 1 to get up into 5th, then knock it down to lean 4-5 so that you can make it 4 laps before pitting. If it's going to rain you should know by the end of lap three.
Then just run around a 4 on the fuel map the rest of the race and you should win by 15-60sec depending on the car you choose. I've still not figured out a way to go either slow enough to avoid the 7th lap or fast enough to get the timer to end before the 6th is up. (or maybe it's the 8th... I always end up between 31:30 and 32:30, running 4:32's on average due to fuel saving)
Edit: It's 6 laps, not 7/8. Also I just ran it in the RX-7 FD (normal road car) medium turbo, racing muffler/manifold/full computer/race transmission + brakes. Full Custom suspension but I didn't even adjust it. weight reduction stage 2. LSD at 11/8/28. Front splitter and wing for aero, both set at about 75% max. Got 2nd but it was only because I didn't have intermediate tires. Tried to pit on the last lap to go back to RH's but that ridiculously long pit time killed me. Ended up closing the gap to 5sec since road cars can murder the gr.4's on the long straights, but it wasn't quite enough. Had I just stayed on the full wet tires I probably would have won by 25sec or more. 2nd with CRD still payed 495k, so that's still pretty good and it was a close, fun race.
So I'd say it's safe to assume any road car that handles well at 650-700pp will have no problems getting a win here. The gr. 3 road cars are probably very easy wins as well. Which makes the re-playability of this race enormous and quite profitable, trying to find the lowest pp car/setup that can still get a win. Sardega Road WTC 800 might be the more profitable race/hr since it takes ~20min for 727.5k vs 32min for 875k in this race, but they both pay well enough that it's efficient either way. Need to try WTC 600 as well, but man I hate the Tokyo course...