Oops, a fly in the pie with the replacement compressor.
This compressor is offered as a "modern" replacement for the old GM A6 ("Keeping you cool since 196X"). The compressor looked good, but as I was installing it I found that the clutch has some protruding bolt heads which would strike the tensioner when the unit turned. I looked at the ad from which I ordered the compressor, and the unit pictured had a different clutch which would have worked. I am in contact with the vendor, to see what we can work out.
If I can't get the compressor with the other clutch, it's back to "Old Faithful" (i.e. the A6). Otherwise, the compressor liked like it would work fine.
One more little glitch I ran into: the filter-drier I bought is slightly larger in diameter than the old one, so the brackets which clamp it and attach it to the front of the radiator housing would not work. I fabbed up a couple of new clamps from some aluminum strips and they will work fine.