Same here, Formula Gran Turismo. It's what I used for A-Spec as well. I figure it stays true to the "Indy 500" more than any other car. Granted, it is a "formula" stlye car, so its more F1 like the two Ferraris, but it's close enough for me in spirit.
I ran this last night in the Nissan R89C with a stage 3 turbo, racing softs and the transmission set to 237mph. Everything else was standard. I used two level 28 Bobs who both have hot temperaments and set the pit strategy to 'off'.
When I checked this morning they had come 3rd, but it must have been close as the mileage covered was 499.97.
I'm not going to give up as a) I don't want to spend 4.7 million cr. on an FGT I'll probably never use again and b) I don't want to babysit them.
So tonight I'm going to raise the top speed, lower the car, increase downforce and try again (perhaps racing hards and one Bob). I think an un-coached win is on the cards here as a small difference may make all the difference.
EDIT: Just for the record, I have since run the Nissan R89C with the specs above but fully lowered, maximum downforce and max speed set to 249mph and it won! No need for an FGT or X2010!
Looks like I might as well splash-the-cash then. My finger did hover over the 'Purchase' button before I just shut down and left for work this morning...