If I was going to do it again I would go small block, the car drives so much nicer on the track (unless you have the cash for the aluminum big block). The car will push on the track and it takes a while to get that dialed in. However, it is nice to have the power without over building, and then there is that cooling thing....... At least I have a hard time keeping mine cool?
Well that is why we build them the way we like them. Just remember to beef up the trans, clutch, and rear end to handle the power.....
Have fun and get what you want!
Brian