Greetings All!
I'm usually in the 164 Department, but now I need advice from you 1800 experts. On Ebay recently, I purchased an SEV/Marchal 55A alternator that was said to come from a 73 1800. I thought that the SEV was pretty much a standardized model among all Volvo's of that era, and it is 90% identical to the 164 units I'm familiar with, except for the rear diode bridge. The bridge is shaped differently and, for some reason, is tinted red. As you'd expect with this French unit, all the threaded studs on the rear casing are metric, including the D+/61 terminal on the left side of the bridge; a 6mm nut goes on perfectly. BUT, the slightly larger B+ terminal in the center is an oddball. Logic would suggest it be 7mm--WRONG. Not 8mm either. NO nut I've tried--standard or metric--works. The threads are a fairly coarse pitch, and don't appear to be mangled or distorted.
Can anybody who has this alternator tell me what thread the B+ is supposed to be? All info appreciated.

Gary in Arizona