Quick advice while I research. Magnum Swap

If you are retaining the Mag EFI you will need the mag flex. My understanding is that one bolt is off from the older ones. Also, you'll want a neutral balance converter, as the flext plate balances the Mag engine

Also, if you score a 67 or earlier TF, the factory converter snouts were smaller, so you either need a converter with big snout, or a bushing ring to make up the difference in the crank register