Welcome to the forum
4.0l Regular Cab Ranger is a rarity, special order from factory, just FYI, Regular cab Rangers were 2.3l or 2.9l/3.0l, expecting best MPG buyers more than power buyers
It should have 8.8" rear end, all 4.0l should have
You can check the door label to see what it has, look here for codes: http://www.therangerstation.com/tech...le_codes.shtml
I wouldn't use studs for the heads in a Ranger swap, unless you can double nut them to remove the studs, tight squeeze in engine bay wouldn't allow head removal with studs in place.
I would add an oil pressure switch for the electric fuel pump with carb use.
'91 Ranger will already have a Fuel pump relay, Green base, that gets Ground from computer to activate it, and oil pressure sender on '91 will be a switch not a true pressure sender.
Just transfer that relay ground wire to the oil pressure switch, which is a ground when oil pressure is above 6psi.
Use a "T" to add "real pressure sender" like PS60, dash gauge in '91 can also be modified to use the PS60 to show "real pressure"
Safety reasons, cuts power to pump if fuel line breaks or engine stalls, EFI computer would normally do that.
Inertia switch is also there for same reason but only activates in a collision.
You can use Chevy type HEI distributor for spark, very reliable, much better than any Ford system, use "coil in cap" models $40-$60, 2 wire hook up plus tach wire
Good info here on parts needed: Ford Ranger V-8 Engine Swap
T5 will be fine, although it's shifter location can be an issue, need custom shift arm bent for best location for you.
1997 and up F-150 4.2l V6 2wd M5OD-R2 will bolt to the 302 block, and has shifter in same location as the ranger M5OD-R1
But it won't have speedo cable hook up, '91 Ranger still used mechanical speedometer
Drive shaft almost always needs to be modified, there are too many placement and trans combinations to say "this will work", you will need to measure and then see if you can find a stock match or get custom shaft.
E-fan is almost a "have to" because of clearance, since no AC you can put the e-fan(s) in front of rad, where AC condenser would sit.
Fan is DC motor so can push or pull air in either direction depending on how you wire it.
Carb intakes usually only have 1 temp sender hole, needed for dash board gauge, you can add a bung to upper rad hose for e-fan temp sender that activates e-fan relay.
You just cut rad hose insert the bung and add a couple of hose clamps.