1965 barracuda charging issue

Your finding diodes missing in a square-back alternator is like my experience in my 1982 Dodge Aries 2.2L. Apparently that was their first application of the square-back in a FWD car. My suspicion is that didn't allow enough air flow to cool the diodes. I would find the 3 positive-side diodes that "hang in the air" gone, almost every year like clockwork. The 3 negative-side ones on a buss-bar that bolts to the case were always fine (better cooling?). That car required unbolting the AC bracket to remove the alternator, which was a pain. Instead, I started splitting the alternator case in half underneath to take it out in 2 pieces. I also started buying just the diodes at an auto electric shop. The guy there said they saw that failure all the time. I started cutting cooling slots in that diode bracket on a bandsaw, which seemed to give 2 years between melt-downs. Eventually that engine had a head gasket failure (endemic) and enough other problems (crazed paint, ...) that I scrapped the car. Not Chrysler's finest decade, and perhaps why you see more Darts than Aries on the road today. In contrast, the round-back alternator diodes are pressed into the case so rarely fail, though my 1965 Newport apparently failed one (rebuilt alternator), and running on 2/3 was just enough to trick me into getting stranded (infamous click-click-click no-crank).