what do you guys think of these engine combos for the wow factor

[norm roll]

im getting ready to make a decision on the engine for my 66 short bed step side.
here's the choice's this is just a drive it every now and then some cruise's and show's.
im kind of after the wow factor for this truck. the chassie will be beefed up as needed for what ever enging i run.
things done so far are as follows most of the frame is boxed in.a x brace in the rear frame rails is already installed. the rear trailing arme are boxed

a tricked out inline 250

a rebuilt 1966 corvette engine bbc 427 _ 425 hp

or a 5.9 cummins with about 500 hp

transmision undecided.