[Short 3/4]

I understand your frustration as I went through this same thing a few years ago. Who would have guessed that brake drums for a Chevy truck would be the hardest part of my mechanical restoration.
I too prefer the original drums, and unfortunately the 3/4 ton 4x4 stuff is unique to that model and just about extinct.
A couple things I learned that you may already know as it looks like you’ve done a lot of research:
All 3/4 ton 4x4’s came with 12x2 drums front and rear, and unfortunately unlike the 1/2 ton’s they are not interchangeable.
There were no duelly or one ton 4x4’s in 66
Sometime in 64 or 65 they changed from a separate bearing housing with slide on drums to a one piece unit with the drums and bearing housing not separate.
I got a lot of help from a guy in Southern California that runs “Drum Garden” not sure if he’s still around, but very knowledgeable and he specializes in stuff that doesn’t exist anymore. Let me know if you can’t find him, I may still have info somewhere. None of the usual parts sources have drums for 3/4 ton four wheelers, I know cuz I talked to them all!
Good luck
Tom