I and other members of my family have gone through a fair share of 2.3 and 3.0 Rangers living in the salty north. 2.3l rangers carry the starter on the passenger side, 3.0 (and maybe the 4.0) carry them on the driver side. The 2.3 and the 3.0 have the same gear ratios but the 4.0 has different ratios and is supposedly heavy duty Therangerstation.com has, hands down, the BEST "tech library" for these trucks. 4x4 came only w the 3.0 and the 4.0 and some of the 2.3's came w 4.10's in the rear. 3.73 is the common number and you can get 3.27 gears to fit (unsure of anything taller) Rangers came stock w 7.5" rearends capable of handling 2300lbs (more than usually, this was a conservative rating) and the 28 spline 8.8" Diffs found in the fx4's were rated for 2800 and if you swapped in a 31 spline Explorer axle you can get 3.08 ratios and 3100 lbs in the rear (more if you rebuilt w better aftermarket bearings) and disc brakes. Rangers came w 9' brakes in the rear(2.3) and 10 inch brakes (3.0 and 4.0. 4x4 or not) in the rear. 93~97ish rangers came w a different tranny support and twin I beam front ends. 98+ got IFS which many components can swap w explorers and 150's. 5.0l 3-core radiators will fit w'o clutch fan installed. Also, they threw whatever driveshaft they had lying on the shelf, so it could be steel or aluminum. The m50d has very simillar ratios to the TDI tranny.
I got a 99 w a stubborn 3.0 (if you can blow one up w oil and coolant in it, you shouldn't be allowed to operate anything more complicated than a refrigerator, unless the bronze distributor/cam position sensor gear lets go). I have both 3.0 and 2.3 trannies kicking around, but I won't be home for alil while.