My 83 Sub is needing to have the AC repaired after a engine swap. I installed the 4x4, transmission, and motor out of my 85 pick up onto the suburban and need to know what the difference is between the two AC pumps? the one that was orig in the sub is larger than the one that came with the reolacement motor. Is there a difference on performance between the two pumps or is one larger because of the dual AC? Which one should I use?

start reading this thread a few pages in. different compressors are discussed. the 85 one is probably the best choice but i don't know if the other will do a better job for the sub
http://www.dieselplace.com/forum/showthread.php?t=305056

thanks I will be using that one.

My 83 Sub is needing to have the AC repaired after a engine swap. I installed the 4x4, transmission, and motor out of my 85 pick up onto the suburban and need to know what the difference is between the two AC pumps? the one that was orig in the sub is larger than the one that came with the reolacement motor. Is there a difference on performance between the two pumps or is one larger because of the dual AC? Which one should I use?

It has nothing to do with single AC or dual (front and rear) AC. Early 6.2s use the large 12 cubic inch axial A6 pump. All 6.2s after 1985 use the smaller, and lighter DA6/HR6 pumps that are 10 cubic inch. Gas engines with V8s use a third totally different radial pump that is also 10 cubic inches.. So, a pump from a 350 gas engine is not going to fit a 6.2 rig.
Later 6.2s after 1985 use the same basic pumps many small four and six cylinder cars use - like Cavailier, Sunbirds, etc.