There was a post here where someone had it done on a DE, of course that p0st would be worthless now thanks to photofuckit.
Im looking into it, on the DE you reportedly can move the A/C bracket up to the power steering hole and it will clear the steering box. I bought the DE compressor bracket for a 240SX on Ebay and I keep checking for a s13 compressor so I can test fit. I was going to use a vintage air underdash unit for the evaporator.
You (like me) have a '74 - so the condenser is a problem. The '75 and later trucks have a different radiator support that allows a larger 3 core radiator and also makes room for the condenser. A couple of the condensers that Vintage Air sells looks like they will work but will take some brackets. It is going to be a tight fit for radiator, condenser & fan in the front. I found brand new factory condensers online, but without the newer support they look like more work than bother, plus they are set up to run on R12.
thats about all I know so far.