One way I got setups was that I downloaded the old ones and renamed them so that they would work in Patch Y. Also had to tweak the differential settings because they were probably made before the addition of preload.
The RAC is probably going to be my favorite car for a while because it feels very rewarding to get it to handle right. I think the RAC is too low in the first place so I upped the ride height to 100 and set the tire pressures to 190 kpa. I didn't fiddle with the suspension settings because I was afraid that I would make the set worse (I have no idea how to set the suspension up. The same goes with the gears.). The set I use now is just a modification to the Race_S set. It doesn't feel as twitchy but the power still makes it want to drift around corners alot.
If I really knew what I was doing, then I would go all out to make the set better but I don't have much of a clue so I went by feel. I use the modded race_s set for pretty much everything, including drifting (I tend to drift with WR sets because they felt more controlled) so my advice might come to a roadblock somewhere.