Where are you getting the term "Diode Trio"? At one time (maybe still) that was a term Delco used for a smaller rectifier that powered the alternator's internal voltage-regulator. The main power rectifiers (six of them) were called the "Rectifier Bridge". This was a "10-SI Delcotron System", new stuff in 1969. As I recall, the starter on my 743 is Delco, so I wouldn't be surprised if the alternator is too. I'll be near mine later today, I may brave the mud and go take a peek... A picture of the other end of the alternator, the wiring end, may tell me more about yours.