I pulling my hair out, looking for the right A/C Compressor for my '77 Corvette. Every parts house web site I go on, including AC Delco's site. They are giving me 2 different part numbers, 15-20206 and 15-21764. Will both fit, the 15-20206 is saying something about a switch. I don't know what to ord...

I have a '77 Corvette and about 500 miles ago, I replaced the A/C hose and resealed the dryer (VIR). We also flushed and vacuumed out the system. It worked great till yesterday, when I was driving and the compressor locked up. Is it just a coincidence, that the compressor went. Or is there something...