Edel air gap+ EFI?

My heads are junk, so im going to replace them. My plan was to refresh the engine next winter and put new or rebuilt heads to it and start building the efi for summer 2018. Because building the engine and Efi at the same time is too much for my wallet. Im going to use 4bbl throttle body. Will the magnum heads bolt right to -68 340 block with no problems and what compression would it have?