89 2wd cab to 90 4x4 frame.
 

how much wiring do i have to do to make the 89 2wd cab work on the 90 4wd frame both are 5.7 motors both are manual window lock and A/C trucks. the 89 has a 700r4 and the 90 has ath400.. i know i will have to move the 4wd shifter. that is where the wiring needs to be added to the 89. something might have to change for the transmission.

Re: 89 2wd cab to 90 4x4 frame.
 

Me, swap the wiring harness from the 4wd cab to the new cab. Not sure, there might be a high humb for the 4wd, which is not in 2wd. Never had a 4WD version of these trucks, so not sure.

Re: 89 2wd cab to 90 4x4 frame.
 

I can't say for sure because I've never tried this. But the only thing I can think of is the differences in speed sensors on transmission, if any difference at all. The transfer case is manual. The only thing electric is the indicator. I'm sure that's simple wiring if you don't have the harness. I don't know about floor hump, but you have both to check

Re: 89 2wd cab to 90 4x4 frame.
 

The front axle connector is electric, run off a switch on the TC lever.

Or you could just lock it in permanently with a 1" piece of 3/4" plastic pipe like I did. Just like running with the hubs always locked in, or like my old jeep that turns all the time anyway from the factory.