engine newb - build me a 331

why would you limit yourself to a 331 when building a new motor?

they even make 5.315 rods for the excuse of "rod ratio" or whatever.

A stock block can take it if its a mild combo (350-380rwhp). A sportsman or mexican would be the next (cheaper) step up.
 
Your first choice isn't bad. But Iskwezm makes a good point. But, then theres the whole idea of getting tired of 400 hp. Being able to upgrade without upgrading would be nice. It comes down to whether or not you have an addictive behavior.I do, 500 hp just doesn't do it anymore.