Howdy Ken and welcome to the forum. Nice to have you on board. Hope you stick around so we can get to know you.
Congrats on picking up an M-500t. It was my 1st Carver amp and still my favorite. (I love the look and the sweet sound.)
I run four M-500(t)s in my main system (all restored) including a non-t bought new in 1982, 2 M-500t's, and an MKII.
(My 2.2 system is horizontally tri-amped with the M-500 driving the tweets, the MKII on the mids, and the "t"s on the subs.)
Most of our service techs work regular jobs so give them a few hours to get back to you on your diode question.
(I'm pretty sure either set will work but I can't address the issue of whether one set will perform better than the other.)