Also just discovered that there is an AC Delco new replacement available for the A6:

You can drain the oil in the A6 by removing the fitting on the bottom sump. But you can't put new oil in like that. To put new oil in, you need to have the compressor off, and stood on it's nose(clutch end). Pour a little oil into the suction side, and turn the compressor clutch to suck it in. You would normally put 1/2 half of the required oil into the compressor, and the other 1/2 into the dryer/accumulator. You can't do that if you have the VIR system(well...not very easily,anyway). So the next best method is to put the remaining oil charge in thru the charge system...same as putting freon in.

I just went out and spun it again and listened real close.  I don't think I'm hearing any noises that would indicate a completely fried compressor.  I do hear some gurgling/ from the box that the hoses go into.  Not hissing like anything is escaping, just some slight gurgling which I'm assuming is due to the fact that I am actually compressing the fluid by turning the comp. shaft.  But, in any case, I believe you're probably right that if the compressor froze up once it would do it again.  Is there any merit to the idea of just replacing the clutch and pulley bearing before replacing the entire compressor?  My thought here is that I could continue to use R12 if I keep my old compressor, but if I replace the comp, I think a switch to R134a would be the only way to go.  And don't you need to replace the drier and other parts if you replace the compressor?  

Dave, I would suggest that you connect your compressor, and with the belt on, run the A/C, and see if it still cools. From what I'm reading, something locked up on it, and you just disconnected the wiring. The bearing on the pulley spins free, and you can turn the clutch by hand. The "gurgling" sound you hear is the liquids flowing thru the compressor, so it apparently still has a charge. If you have a set of gauges, or can borrow them, see what kind of pressures you have on both sides of the system(high side & low side).

I am about to do some major work on my 1969 427. The original harrison unit developed a leak so I put an aftermarket compressor on the car.  I want to restore the original compressor. Any suggestions on who can overhaul these units. I am in the tidewater area of Virginia.  Thanks, Bob

Thanks for the advice, Joel.  I am in the process of doing a radiator replacement so I plan to put the A/C belt back on and then hook up the connector and see what happens.    Can't hurt to try.  Well, I could be out another belt, but it's a cheapie.  If/when I ever do get A/C working I'll put on a reproduction belt (going that way now with my alternator belt).  I'll post again after I get it running.  

It's not the pully you need to turn, it the center hub of the compressor in the middle of the pully.  That will tell you if the compresser is seized.

The center hub turns on mine.  The compressor is not currently seized although as Joel mentions it may have seized at one time.  I'm just going to hook everything back up and see what happens.