I swapped a carb onto my 4.6. All you really need is a fuel pressure regulator, a carburetor, and possibly a different intake. I am not sure what the stock intakes are like on the old 5.0 EFI engines.
What I do know is that the plain old Carbureted 5.0s made more power than the EFI H-O 5.0s did haha. Even with just a stock carb setup from 1985, it made more power. EFI is not the end-all-be-all like everybody things.