I did this exact same race last July, I got a 1.03.705, 100% clean. I'm sure I could do better by now, probably break into the 1.02's with some time investment.
The thread for it already exists in the OLR section here:
I wish I had the 787b. I'm one of those losers who is only about 6x% done with the game, and the only 'fast' car I have is the F090, which is way slower than the F1 cars my friend has. I manage to get a 1:06.xx in an endurance race with the F090... that's about the best I could muster