I'd go for the Mark IV  ;). I got the C9 in the UCD for more then I bought the 787b for, i dont remember exactly but I think it was around 5.5million.

I'm leaning to the Mark IV as well, mainly because it's the only one I haven't driven yet.

5.5M is manageable. Either 5 B-Spec Dream Cup or 2 hours of American Cup Indy Race with my ZR1 RM. And there's the seasonal events for next week as well xD.

Yup, I use those 2 events for grinding credits as well, I've been trying to get the 10M trophy for a while but every time I see a nice car in the UCD I buy it :(, I'm on my way to buy all the group C and LMP cars right now they. I've heard good thing about the Peugeot 908 HDi FAP so that's next on my list.

Damn I really need a wheel as this DS3 is cutting at my GT5 overall enjoyment bar. 

Done yet?

What's the reward? Which car, I mean?

The only car I ever use for farming, other than the ZR1 RM, is the X2010 on B-Spec. My Sebastian Vettel livery one has already 6K Km

You should really consider a wheel, it makes the experience much more complete.

Not yet, I've entered the last hour just now  

Updated the OP with the 23rd hour mark report.

Man you have super human skills to do this all on your own, I mean the real le mans is completed using more the one driver :P. 

I plan on getting a wheel as soon as I can get the money. I use the ZR1 RM for the A-spec indy and the FGT for B-spec Dream Car Championship. I haven't gotten to lvl30 yet in a-spec to get the X2010 and i'm afraid that I might not be able to complete it with my DS3. =

Nahhh, I just had a lot of free time this weekend and a lot of patience as well

The Sebastian Vettel challenge is doable with a DS3, but I haven't seen anyone get beyond silver with it. Everyone I've read over at GTplanet, who have the Gold on that challenge, were all driving with a wheel.

Heck, even with a wheel, getting gold on Suzuka was almost impossible for me >_<.

I have the Driving Force GT myself, bought it for GT4 actually. Is it any good with GT5? I really want to play with a wheel! How do you make the pedals stick though? The only way I know how to is using them on a carpet so they don't slide away when you push at them.

Done yet?