Two suggestions.
First, my W126 ate alternators until I found a loose connection in the main alternator feed wire up to the secondary firewall. The nut was loose on the stud for the big wire and it let the current spike as it made and lost connection.

The second one is that I found a place here in Vegas that made me a custom alternator from new Delco parts for only $195. It almost bolted right in, I needed to whittle on the mounting bracket with the adjustment bolt just a little. I now have a 140-amp alternator that is easily rebuilt, except that it puts out so much power that I haven't needed to fix it yet!

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There is a very fine line between "hobby" and "mental illness."
FrankenBenz: '87 560SEC with an '02 cammed LS6 and custom 4L60E.
Bling: '87 560SEC, ported/polished, lowered
Lisa: '87 560SEL, lowered