Alright, update:

It turned out it was the bolt squeezing the "ears" together, which was causing the alternator to lock up. My old alternator had no issues, but the new alternator casting was slightly wider, and the spacer was more "sloppy" with enough play to allow this to happen.

I placed a washer next to the spacer and it worked fine.

However, the long arm adjustment bolt hole was "wallered out". So instead of tapping for a bigger bolt, I put my old alternator back on and it runs great.

I did notice that the alternator is charging at 15 volts, but maybe it was just charging a slightly drained battery. I replaced my voltage regulator with one I had laying on the shelf, but that one only would increase from 12.6 up to 12.63 with the engine RPM's raised and the amp meter on the dash was jumping around.

Long story short (and a discussion for another thread most likely), I returned the original regulator to its proper place and its charging again, although a little high. I'll dig into that later.

It was the bolt squeezing the alternator case and locking up the belt. I have never had the privilege of experiencing that before.

Thanks for the help, I really appreciate it.

Eightlitermopar