I'll say it..
Something must be wrong with the engine,...
Unless you buying a crate motor,.. selling this engine and saying its been gone through and nothing is wrong with it,.. and THEN SAYING your only selling because you want EFI,.. throws up all kinda of red flags. Particularly if there is nothing wrong with the long block.
Doesnt make sense. If you want to go back to EFI,.. there is your motor,.. you say it runs great,.. then convert it back to EFI. It started out life that way.
Hurst