'88 TC swap into '83 5.0

I'm not sure about all the other stuff, but I do know that a Thunderbird gas tank won't fit in a Fox mustang (too big), and if the '83 was a four speed car then you will have to get a different driveshaft. One from a later model 5 speed mustang would work though.

Oh, and this is a minor thing, but just remember that the Thunderbird is set up with a hydraulic clutch, so you will have to swap bellhousings if you want to use a cable-operated clutch, and Thunderbirds have an electronic speedo drive as opposed to the cable drive on Mustangs. Also, the transmissions behind Turbo engines have a 7 tooth speedo drive, vs 6 tooth for naturally aspirated cars, so you gotta make sure you get a turbo-specific cable speedo drive.

Remember that you can swap all the Thunderbird's brakes over to the Mustang, but you'll want a bigger master cylinder (which will be easy since your car already has a 2-port master...a good one to pick up is one for an '85 Lincoln Town car, 1" bore, you can get it for about $20). The four wheel disc would be nice though