Welcome to the board.
Also look at the rear gearing as well. As others mentioned the 305 is a alright engine for to and from but a 350 would defintely be a step up. But then it may be needed for a new radiator depending on how much core capacity it has.
The TH350 would be a ideal replacement for it but a TH400 would also be good. 700r4 with lower gear ratio like 3.73 or larger numerical may be better but depends on what your use of the truck will be.