Nacho,

I think you are the expert on this but here goes.

Easy fit and cheap is a mid 70's late square back factory rated at 78 amps. Similar (but more reliable than reman) is the 75 amp Powermaster squareback. Next up is the Tuffstuff 100 amp square back. All available in 3 wire and all limited to 50 or so amps at idle. Not sure how long the Tuff Stuff 100 amp unit would last running at 80 amps most of the time.

In GM cases, the small "10" case 140A Powermaster unit is nice... but it is longer than a square back and output stud may hit the head (mine did, BB, returned it). A GM specific 100 A alternator is low cost and may need a different top bracket (no AC) or no go (with AC). Most of the GM case offerings are 1 wire. Not sure about the ALT light with a 1 wire. The larger 12 case GM's with MOPAR mounting are supposed to fit better but no personal experience and very expensive from Powermaster.

That leaves the "green" alternators you posted about some weeks ago. Lots of output and expensive.

If high continuous load is not a requirement, maybe the 3 wire 100A Tuffstuff which can be serviced with any squareback in an emergency.

Or if not AC get a generic GM 100 amp unit and change the top bracket (generic) and cut spacers if needed.

Good luck!