Well.......... Look at it this way, if you want to get maximum efficiency out of that 4 inch bore. It makes sense to use as muck of the bore as possible. A 350 stroke is 3.48 inches and a 327 stroke is 3.25 inches. So you will be replacing crank and pistons. If you really want to get power And since you are replacing the crank, have a look at the 383 stroker Kit. They are quite resonably priced.