Rare Vintage Power Wagon Has Modern Diesel Power
fordcummins.com - Increase Horsepower with Ford Cummins Diesel conversion kits
http://www.4btswaps.com/
I know you said gasoline... but it needed to be said.
Aiming for fuel economy and ditching the EFI is like trying to run a marathon in Army boots. You might be able to make it, but you're adding a huge challenge for no good reason. I rarely see carbs on modern engines at the classic car shows I go to, but it does happen every now and then.
If you gotta stick to Ford and gasoline... maybe the new V6 Ecoboost from the F150?