89-94 A4LD transmission is the same behind the 2.9L or 4.0L
PHYSICALLY
However they are not as strong internally in the earlier years, putting a 89 trans in a 92 truck is working backwards, I personally would use the lowest mileage and latest year trans I could find, or consider a rebuild (A GOOD REBUILD, do some research on this forum for the dreaded a4ld)
putting a 94 explorer a4ld in your 92 Ranger is a bolt in deal, your wiring remains.
The A4ld only has a few wires and a kick down cable.
the 4.0L is a bit more work, and some wiring.
You need to do some research, these topics are covered in detail over and over on this forum.