My 2.3 has seen better years so I am replacing it. I have a 4.0 out of an automatic 97 explorer. My ranger has a manual trans (1. Can my trans handle the 4.0? 2. Can my current diff handle the 4.0 and stock manual? 3. Flash the 2.3 computer for 4.0 or just swap them out?) If your answer requires more info just ask and I will do my best.

 

The 2.3l Manual transmission can't be bolted to the 4.0l engine

In 1988 2WD Rangers got the M5OD-R1(M5R1) manual transmissions
The M5R1 has an engine specific main case, i.e. the bellhousing is not removable its part of the main case
The 2.3l, 3.0l and 4.0l engines all have different bolt patterns for transmission, while these are all M5R1s internally they have different cases, 4.0l models also had different gear ratios
So you would need an M5R1 from a 4.0l engine, 1990 to 1997, as these have the speedometer hookup, 1998 and up do not
Also 2WD version, as a 4WD version wouldn't work in a 2WD vehicle

Yes, you need a 4.0l computer and its engine wiring harness, 1996 or 1997, from a manual transmission 4.0l, as manual and auto computers are different
1995 would also work but was an oddball year for Ranger computers, first OBD2 model
1996/7 because fuel system was changed in 1998 so those are the least trouble to match up with 1995 fuel system

Also need exhaust system

Doing a V8(5.0l) swap is EXACTLY the same work, engine, transmission, computer and engine wiring harness
And V8 swap is well documented, lots of info on the mechanics and wiring

The 4cyl to V6 is not done very often, so not much info on the mechanics and wiring interfaces needed
This is because you can just buy a factory V6 Ranger, usually cheaper than the cost of the swap, for sure in time cost, but also money as the bits and pieces needed add up

Just a heads up
The 1995 2.3l Lima engine was the first year of the new crank sensor design, so can only be swapped with 1995-1997 2.3l Lima or the 1998-2001 stroked 2.5l Lima engine
Can't use 1994 or earlier 2.3l Lima's