finally it looks like V-8 time

I was thinking about chucking the manifold and adapting the efi to a 4bbl manifold. maybe it isn't worth it, I was just thinking it might have an advantage in mileage and reliability over a 4bbl.

Carb is easier, LOL;

do you have the computer and the EFI dist for the computer setup already, and the associated wiring harness?

you will need to run a special higher pressure electric fuel pump.
you will need a return line to the fuel tank, { you can cut the fuel filler tube and tap into that.}

Your manifold looks like it has the special EFI style water temp sensor. :)
what about the MAP sensor? did Mopar use an Air density sensor?, {was that in the air cleaner setup stock?}

Yes you Can go to EFI, even aftermarket, like from Summit,
but a carb is simpler, and cheaper.

I am using a 600cfm Edelebrock # 1406 on my 318 in my '64 Valiant.
I get about 20mpg on the road, if I stay under 75mph.
2.93 Sure Grip gear,
205/70/r14 tires.

Its wise of you to ask questions, Before you start buying a lot of your parts.

Take time, and be careful, and take photos. :)