I did a bit of hunting around after checking out the Chevy forum (I also play with an old truck, as well as my tractors). I found this on an air conditioning company's web site as the temp that they would expect from one of their systems:
3. CENTER DUCT TEMPERATURE ( 36-46 DEGREES F.)
Don't know how that should translate to a system on a tractor, but I'd guess that 60 degrees is a bit on the high side. They do have different numbers at various RPMs for the compressor, but the output temp remained the same.
On the other hand, that's lots cooler than the air that hits me on my non-cab, non-conditioned tractor /forums/images/graemlins/grin.gif /forums/images/graemlins/laugh.gif. But for a new unit, I'd expect that at a reasonable 85 degrees that it should turn your cab into an icebox.