Homemade EFI, what manifold?

You can get an M1 with the injector bosses already drilled and made for a 4bbl. They have adapters so you can also bolt a stock Magnum style throttle body on top or you can buy an after market 4bbl throttle body. That's the route I would go, do some searching I just bought my MPI 4bbl M1 for 218 brand new shipped off of Ebay. Oh and you can use the stock magnum injectors and fuel rails on the M1 as well.