Nope, I've got no R10, it's a hopeless car, really - I used to have one as I won it in my first level 21 ticket (winning extreme A-spec events) and got really excited about it, but once I tried it on Indy it was soo slow compared to the MINOLTA. Traded it for the F2007 if I remember right, so it wasn't so bad after all
The R89C is just ... all wrong, perhaps if you've got a masterpiece of a setup I would consider trying it again, I can't get it to perform - it feels slow and heavy compared to the others, but very stable!
The GT-ONE lap is a wonder-lap - nothing can come close to it, but as the Sauber's lap time have increased I rank it highest along with the R8 because of their handling which is a bit better. Have also done a GT-ONE vs Sauber on Nordschleife, the GT-ONE won the first round with a time of (I think, this is memory only) 5.47, the Sauber with 5.52.
908 vs Bentley... I think the 908 is faster - the Bentley is a bit hard to drive fast around the track, but the 908 I could do many laps under 1.15.
Let me know if you're are on the lookout for anything, I've got +10 mil credits thanks to seasonal events and absolutely no time to play (meaning no time to spend all that cash)!