Alternator overcharging

If this is a solid state regulator it very likely is NOT a bad regulator

HOW did you check voltage drop? The way I do this is follows:

Access as close as you can get to the regulator IGN terminal. Do not disconnect anything, as you want the current load to be "as normal." Usually, the ballast resistor "key side" is what you want. Probe that and the battery POS, with key in "run." ANY drop there is added to the VR nominal set point of 14, AKA if you read 1.4V that would be a charging figure of 15.4.

ALSO CHECK ground drop. Run this check running at "medium cruise" RPM both with accessories off, battery "normalized" and thane again with heater, lights, etc, running

Stab one probe into the VR mounting flange. Stab the other into the top of the battery NEG post. As above, you want to see the less the better, zero would be perfect

IN RARE CASES I've seen claims the battery itself caused this problem, so you might swap in a good know battery to test