Since you seem to want more power fo a 70s full size car and have budjet/plan to go the efi route----I would suggest that you use a Dart SHP block and build it with a 4.125 bore---new block, 4 bolt mains, etc-------

Your in Atlanta so you could source your stuff down at Summitt------------

However, before spending a wad of greenbacks on doing a efi for an early type engine, I would suggest that you contact John Tucker at Southern Performance systems for a kit to put in a late model LS type aluminum engine---tell him I sent you-