[Jim Vander Wal]

The T56 Magnum will fit. I'd go with the .6x whatever 6th gear OD not the .5. I think the coupes have the Dana differential with 3.46 gears.
You'll need the appropriate bellhousing, An aluminum Ford or QuickTime steel would work, talk to your provider.
I like the McLeod RST or heavier duty RXT.
You'll need a shorter driveshaft.
Pull the engine. I've been party to doing the swap with the engine in place. Never again.
The shifter may be in a different location.
Jim