Blowing voltage regulators
The fusible link for the upper contact melted. So if I'm reading correctly the problem is not enough resistance in the alternator and replacing the fusible link would not solve the problem.
Correct.
Might as well buy one of those new alts with the built in regulators.
Whoa! Hang in there. There's some potential problems with that solution.
Maybe I should have written "mostly correct". It could have shorted before the alternator.
With the fuse to upper contact blown, we know two things.
1. The electromagetic coil in the regulator wasn't pulling very hard. In other words, the voltage was low.
2. Too much current went through the regulator because it found an easy path to ground.
So here's where to look next.
a. The connecting wire from the regulator to the alternator's 'field' terminal. If any part of that wire touched a ground, even briefly, while the key was in run, that would melt the fuse.
b. At the alternator, if any part of the field circuit grounded. Can try to check with a multimeter. We can walk you through that.
Visually, check the field terminal (the one green wire plugs into) and the brush and brush holder. The brushes and brush holders are easy to replace.
If the slip rings or rotor windings are grounding that might be best to have fixed at a shop.