Either will work , machining the crank costs a few $$ , it will need to have the mains cut down to the smaller main journal size & it will obviously need to be balanced so you need to see what that would cost compared to buying a new part , for $150 440 source will balance the kit + you get new rods with high strength bolts . What I am saying is it may not save any $$ to rebuild the old parts & just buy new pistons so check pricing carefully .
The power potential is high , but horsepower is like a piece of string , how long is a piece of string ??
How much $$ do you want to spend ?? I am sure you could make more power than you will need with Indy heads & a solid or roller cam , big carb & headers , It is all about air flow in & out ultimatly
