New battery. New alternator. Weird symptoms not charging

Hi everyone. Hopefully i can get some advice regarding my issue. I have a 91 2.4 mm. The alternator wasnt charging the battery. Found that the stud in the alternator where the power output connects was totally fried and loose. I also found the fuseable link for the alternator in the small box connected to the positive battery terminal was fried.

So i replaced the alternator with a 75 amp alt out of a mits van and replaced the battery. The alternator still shows 12.4 v output. Im going to test the alternator at autozone tomorrow but am at a loss as to where else the problem could be.

This might be a ground issue or the main leads off the battery or power into the battery from the charging circuit is bad. go through them with a multimeter and check continuity and resistance. It should be showing more than 12.4v - try getting a voltage reading off it when you're revving the engine and see if there's an increase in output.