Double check me, but I believe the stock alternators are the same. I checked Advance Auto Parts site and found them to be the same part #'s. The 3g I have is for a 92 ford van 95 amp, but when I upgrade next time, I'm going for the 130 amp used in say a 94 Ford Van 5.8 liter. Same housing, all I had to do was buy a bolt for the top ear.
It the same alternator but the clock positions are different. If you take the 3 bolts loose you can rotate the alt mounting bracket.
When swapping the alts. the harness will get real short.
years back when my GTs alt died I bought a new 4 cylinder alt (back then 5 amps higher and 15 bux cheaper) bolted it right onto the GT with no problems.
When I did it years back I was told the 5.0L got less amps due to the fact it had the mechanical cooling fan. While the 2.3s got the electric. Well my 5.0L had an aftermarket electric (WELL WORTH IT!)