What do you think it could run?

I love my Duster, I think it so cool with Road Runner engine in it (at least the size of the RR engine). I agree with what Cudafever said, that making it faster is part of the fun.
Never the less, it will be interesting what it runs first time out. I still have some things to fix and improve before I go, so we shall see. Thanks again for all the interesting replies.