The motor is pretty much the same under the intake manifold, so you should be able to swap the car stuff onto the efi (and vice versa) on your 2.3.

As you guessed, there is a difference in fuel pressure (and methods --the EFI uses an electric fuel pump and IIRC, the carb uses a mechanical pump). You'd need the appropriate ECU and engine harness, and I'm not sure whether that extends to parts of the body harness (guages and such). I'd suggest just swapping the block and head. You'd probably get a little better mileage with the late-model EFI, but IMHO, it is more trouble than it is worth to upgrade the rest of the truck to match the 94 EFI and intake.

Randii