[gmachinz]

I would suggest thoroughly troubleshooting the stock system before throwing oddball aftermarket parts and money into it. I've restored/overhauled and seviced a lot ofbstock GM ac systems over the years and while you can improve on older systems somewhat, I have never understood the desire to completely toss the GM setup and go aftermarket. Imo, there is no need to do that. Compressors work off pressure, read by both low and high switches. Some years have ranco switches too....then there is the issue of a clogged orifice tube, bad/weak compressor, maybe even faulty low/high pressure switches. You may just be low on freon.

On something as unknown as a 37 year old AC system, lets face it-the whole system could use an overhaul. And parts are still readily available too. Keep the AC system stock and simply overhaul it-it really isnt too difficult to do.