
Just get any Fairmont for parts. 9 times out of 10, it'll be an I6 powerband. 9/10 it'll be a C3.
Hi mount 3.3's fit Mustang Foxes with just the 78 to 83 Fairmont 3.3 x-member, and you can use the Mustangs Cologne V6 gearbox or the stock Fairmont gearbox. Each is the same 2.8 or 3.3 except for the bellhousing/flywheel/pressure plate. Ring gear is even the same...138 tooth because the US 3.3 used a German automatic gearbox.
If its auto, Fairmonts and Mustang 3.3's used the same C3 gearbox used behind 1974 to 1979.5 V6 Mustangs.
If its manual, the gearbox varied between the SR4 and SROD, but with the right bellhousing, it bolts to the 3.3.
Fairmonts/Cougars/Granadas/Mustangs/Capris generally ran high mount blue engines. Low mounts were powder gray and used a C4 gearbox. California spec were high mounts, but there were a bunch of low mount blocks used in automatic applications in 1981 Thunderbirds and some selected Lincoln Mercury Fox bodies. Cougars and some Capris.
The X-member just has elongated horns at the front to suit the I6.
All Fox 3.3 sumps were same, lots around!
Good luck, the old Fox is a lot of fun