are gear ratios diferent between 1991-1993?

I have a 93 Jimmy SLT, 4x4, vin W, 4.3 vortec, pushbutton 4x4 and also picked up a 91 Jimmy SLE, 4x4, vin Z, 4.3 TBI, floorshift 4x4 for parts.
I want to swap out the rear end on my 93 with the 1 from the 91.
The axles are diferent as the 91 has cogs @ the wheel end for ABS sensors attached to the backing plates and the 93 does not. Also the wheel cylinders on the 91 have clips to hold them in and the 93 has 2 bolts.
I will be swapping the backing plates.
now my question is .. will the gearing be the same in both rear ends or will I have to swap out the front diff as well so i dont tear every thing apart using 4 wheel drive?
(I have to pull most of the front end apart anyway to change cv joints .. so whats a couple more bolts ?:lol: )

Another question..
Can I flip the rear end around and mount it to the underside of the leaf spring instead of on top ? that would give me a couple inches of extra clearance.

Thanks in advance
Steve