Re: xf mpfi question
You can't do a 1:1 swap with just the intake gear. If you want to put a carbi into an EFI engine, you also have to get yourself a carbi head (amoung other parts).
The EFI head has a compression chamber volume of approximately 96cc while the carbi is only 92cc. This would suggest the carbi head offers better compression, but I think Ford fitted different pistons to the EFI engines to counteract this. The EFI head also has better flowed ports that are more friendly to the EFI system, particularly the intake rams, than that of the carbi head.
Also, to stop you from doing a direct change (or at least make it more difficult), the EFI heads have a small cut-out in the upper right of every inlet port where it bolts to the manifold to allow for the injector. The bolts may also be further appart to accomodate for this on the EFI heads.
If you do this and attempt to remove the computer, you'd have to make sure to fit the carbi engine's distribotor and fuel pump (and the cam to run it, as smee says). The former because the ECU controls the spark advance via a 6-wire connector (only 2 wires enter the carb dizzy), and the latter because the EFI engines run a high-pressure, in-tank fuel pump, which is also connected to the ECU.
With all that being said, I'm very curious to know why you'd want to remove the EFI in the first place. Unless you're getting into some very serious modifications (stage 3 cam, etc) then the EFI engine is going to afford you a lot of luxuries that the carb simply cannot - Increased power and torque outputs to the tune of 30% or more, easier to start, no worries about tuning, not to mention that the factory injection system can provide about as much flow (when called for) as a 420 Holly without flooding the engine in the process. It seems like a lot of hassle for something un-necessary.