Lots of things to consider: First, a quick search, I could not find a price for a REAL, new, York AC compressor. The aftermarket copies, new, are $300. How much is he telling you the new compressor is going to be, $500? Plus installation? Plus AC service? Just curious. Rebuilts are 250-ish, but they don't say what brand!

A new rotary Diesel Keiki can be had for under 250. Aftermarket units are less. Rebuilts are less. It's a commodity, lots of options.

To do the conversion requires that all the old hardware be removed, a later bracket sourced (very common) and installation of all. Your hose ends will need to be changed. Any AC shop worth it's salt has the equipment to do that. The hoses should be plenty long enough, don't need to be replaced. Your Saginaw AC pump can be made to fit. Not a huge amount of labor, and not that much worse than getting an old York out, and a new one in. My 82 245Ti still has it's York compressor. The AC is running R12 and it's great, but the dang compressor is knocking like crazy. One of these days it's going to seize, and it's all coming out. Rotary for me.

The later style compressors are so easily changed, your guy should not be averse to putting in the rebuilt unit, later style, the rotary. Or, maybe he just doesn't like rebuilts, for whatever reason. If that's the case, maybe you should get another quote. If he tells you he won't do the swap, you should definitely go elsewhere, at least to ask.

The biggest advantage to going with the later compressor is the ability to run R134 refrigerant, which is 1/3 the cost of R12...maybe even less. The Yorks don't do too well with R134--don't remember the science of why.

There is a ton of noise out there saying do NOT run R134 in the pre-91 systems (which have a better condenser). I'm here to say bunk. No, it will not be as cold as R12, and no it won't be as cold as your 2002 Chevy. However with the correct, R134 expansion valve, we run R134 in 240s from 90 back with great success, and we live where summer temps are regularly over 100. Properly charged, the systems discharge at 55 or below at the vents on a hot day. If idle temps are a problem, install a condenser fan. We just redid the AC in a 79 245. The car has a 92 system in it with a serpentine condenser and condenser fan, running R134 and a rotary compressor. Discharged at 55 degrees on a 90+ day, at idle!

By the way, the rotary compressors aren't really rotary. They just look like they are. They have pistons in 'em.