I'd go with a GM alternator. I ended up getting a bracket from a dude on Pirate who makes them. Although, I have not painted and installed it yet. It's designed for the one-wire 12SI, 10SI and CS130 type cases with V-belts. The CS130 is typically 105-amp and found on late 80s GM V8 RWD cars and trucks, usually ones with a 5.0L 4 barrel, for example a 1988 Caprice.
If you want to stay sorta true, the 12SI was 94-amp and sometimes uses 8mm mounting hardware. That was on a ton of 1984-1987 GM cars, for example the 1987 Buick Regal 5.0L had the metric 12SI.
I'm waiting until my alternator gives up because my Optima finally died recently and that dinked the checking account replacing it. No sense removing perfectly functioning alternator at this point. That battery was an Aurora-made Optima blemish that was at least 8 years old. Got my money's worth out of it. Plus I figure if my stock 23 year old 60-amp OEM charging system kept that Optima alive that long, it does not deserve to be unceremoniously tossed.