Re: upgrading the alternator for higher current capacity, the old adage applies, "Too much is always better than not enough!"

Current is a "pull" or "draw" from the demand side, so amperage ratings on the supply side just indicate how much demand they can safely meet and handle -- i.e., don't worry about an alternator "putting out too much amperage".

Voltage is a "push" from the supply side, so as long as an alternator has a suitable voltage rating for a typical 12-volt passenger-vehicle application and can meet or (preferably) exceed the expected current demand, you should be fine. At worst, you might spend more than necessary for a higher current capacity than you really need or would ever use.

Also check/refurb your major grounds. Not sure how similar yours would be to my '87, but I've got 3-piece ground cables going from my battery negative to the body (inner fender area below the battery tray), from there to the frame (inner side of the main rail along the lower wheel arch), and from there to the block, plus another ground from the head to the firewall.