1981 Vett help

Ok my friend just got his fathers 1981 auto vett. The car is in pretty good shape and its only got 48,000 miles on it. However it dosnt have enough power for him. So what should he do to it? I suggested an engine swap. I know a little about domestics but when it comes to what engine he should put in his car I have no idea. We went to the GM web site just for fun to see what they had for crate motors and we are thinking of something along the lines of a small block. Maybe the 350CI 290hp HO engine? Its only $1599.00 and sounds like it has good potential. Or should he just start with a plain block and build it from the ground up? His goal right now hp wise is like 400hp... but you know how that goes those numbers always seem to get bigger. So what do you guys think? Should he stay with his stock motor, swap in a prebuilt motor, or build a new motor from the ground up?

Your right! Vettes of this vintage only have around 150hp. Crapy!! With the low miles that you mention you could probably do a cam/ head/ intake/ carb/ exhaust upgrade to get good hp. With that kind of power don't forget about subframe conectors, don't want to twist it up!!!