The TK is several inches shorter than an M5OD.
In an 86 here are the mods you will need to make:
Clutch hydraulic line will need changed, it won't mate to the M5OD slave. I'd just get a whole set and replace it all.
The transmission crossmember needs to move back. If you grind out the rivets that hold the mounting ears and remove them you will see the second set of holes. The ears and crossmember can be reused, they just need to move. Reinstall the ears with a set of grade 5 bolts and nylon or stover lock nuts.
The driveshafts have to change length. If you are keeping the BW1350 transfercase find a set of shafts from an 85 or newer 4x4 that had an A4LD automatic. They will be the correct length.
Your shifter hole may or may not need to be modified. Your floor patch plate almost certainly will need to be.
Your speedo cable will need to be changed for a longer one. Again, parts from an RBV with an A4LD will work.