To the OP:
Searching for "+4r70W +tranny +swap" will give you tons of threads to search thru for info.
Almost everyone here has swapped, modded, or otherwise upgraded the original transmissions at this point.
I went thru this years ago; searching my post will give you pretty much all the info that's out there, because I went back and corrected most of my stupid questions and bad info.
Any post that takes more than a second to parse isn't going to get an answer from me; it's pretty easy to be clear if you want to be.
Short version of Transmission swap:
Up to 03 4R70W can be used; an 03 may or may not have the gear on the tailshaft, to use it in our cars, it must have this gear.
A professional can successfully swap the tailshaft; if you're a noob posting here, most likely you can't.
You have to replace some internal components with parts from the original transmission; you need both, apart, side by side at the same time.
94/95 need the electrical guts, or serious rework. See Jerry's thesis.
You have to repin the harness for most swap combinations.
This is just the Deal-Breaker Sh*t.
There's a lot more to find about this here, if you
Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.
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