I know you've all heard the expression before, but just to remind you-
Never ever ever ever sell a car to family or friends.
I've done it a few times and it has always given me grief- hearing about mechanical issues or dealing with issues of disclosure...
Just trust me, its not worth it. Sell the car to someone you don't know and as issues come up- which they will on every car on the road- they will deal with the issues without your involvement.
I'd rather deal with an annoyed friend when I tell him I won't sell him the car than risk the friendship when the motor blows in a year (or whatever).
Maybe a race car is different, but I sort-of doubt it.