Let's put it in terms of what you plan to do with the truck.

If you are just looking for a good running cruiser, get yourself some 305 heads and intake and build the 305 back stock. That'll be the easiest on your wallet.

If you will be a regular at the drag strip, build a 350 or a 383 for it.

Don't waste your time, money and effort trying to hot rod a 305 in my opinion. Follow Dave's rule, there's no replacement for displacement.