[Pontiac62]

I've been looking into replacing the compressor in my 62 GP. I have the original A6 compressor made by Frigidaire.
Besides the pulley diameter, there are a couple of things that I'm finding different in various compressors, even though they claim to be direct replacements. One is the clocking of the wire connections. The one I have is clocked at 10, while most of the replacements are clocked at 2. It doesn't seem to make any difference, but there is also one dimension that varies. It is called "mount distance to groove midpoint" .I have found that it varies from 1.9 in to 2.1 in. There is no reference drawing to show what that dimension is. Does anyone know where that is measured?
thanks,
Les