1965 barracuda charging issue

"It might be" that poor ----REALLY POOR---- connections in the charge path, including the ammeter, the bulkhead connector......are suddenly causing "spikes" in the charge current and are "killing" diodes

One easy way to troubleshoot this would be to temporarily "rig" a small test wire from the output stud on your alternator. One way would be to connect it to a voltmeter if you have one for a spare for a week or so. Another would be to use a 12V indicator lamp of some sort, even a dash lamp. You would need to rig it so you can disconnect when not driving, so a switch. You would need to find a way to run it into the pass compartment

So, example: Connect to alternator output stud, a small fuse holder say, 2A fuse, use small 18 or 16 ga wire. Run into pass conpartment, connect a small 12V test lamp/ indicator lamp. From the lamp run back out into engine bay and connect straight to battery through a second small fuse. Starter relay "big post" is a good place

If the lamp glows dim right after starting, this is OK. Shows a small amount of voltage drop in the charging path to the battery. What is BAD, which would show poor connections along the way, is a fairly bright lamp, or the lamp "blinks" bright/ dim at odd times, showing a connection making/ breaking

If the lamp burns out YOU KNOW there is a bad connection LOL