With the addition of high powered stereos, lighting and other electronics we find the need for an alternator that can produce more power than the stock alternator typically found in Rangers.

The 1997 F250 5.4 V8 alternator works on a 1991 4.0 STX 4x4. Bolts, belts and wires same. The person making the swap tinned the leads on the power output into one wire.  You must also cut the black/white and crimp on a connector to run it back to the 1997 alternator.  Not hard at all.  80 amps to 110, not 130 but that's ok, it's done.  

The 2.9 and 4.0 alternator mounting is different

On the 4.0, 4.2 (F-150) and later 3.0 Aerostars and Rangers, the alternator is "fixed" because there is a separate belt tensioner.

The 2.9 uses an "offset ear" alternator.  Other applications that use the same alternator case are the 1.9-liter Escorts, 2.3 Tempo/Topaz and 2.5 liter Taurus.

The Escorts can have anything from a 40amp alternator to a 90amp
The Tempo's will typically have a 60amp or a 75amp.
The Taurus's will usually have a 75amp alternator.

A 130amp alternator from a 1986 Mercury Grand Marquis is said to be a direct bolt on for a 2.3 and not require a pulley change.

There is also a 90amp alternator built on the small diameter internal fan case but with a pivot mount that will bolt to the 2.9 engine brackets, look on later Ford Tempo's.
The problem with this alternator is that pulley alignment is a serious problem.

There are 95 amp models in:
1991-1994 Aerostar and Navajo 4.0
1993-1996 Bronco
1991-1999 Explorer
1994-1997 B-Series (All!)
1992-2001 Ranger (All!)
1997-1998 Tracer and Escort (95 amp)

To upgrade use the 130 amp model found in:
1996-1998 Explorer 4.0 (130 Amp Standard)
1998 B-Series (all!) (Optional 130 Amp)
1996-2001 Ranger (Optional 130 Amp)

Although the 130 Amp is physically larger than the 95 Amp (good way to make sure you have the right one!) it will drop right in!  Same bolts and belt!  20 minutes for 35 more amps!