Ok, here they are. 67 GTX 440I had the Raybestos 36221 on my 66 Plymouth with 10" power drums and it worked well.
But you are correct I think manual brakes would be a different bore size, but he said he ordered a new booster so I knew he had power brakes.
I think front discs on a 66 are extremely rare and that master would have a larger reservoir section for the discs.
Pwr Disc rear drum NMC22774
Pwr 4 wheel drum NMC11373
Manual 4 wheel Drum NMC11373M
Hope this helps someone out. I ordered the PWR Disc one for my Hemi Belvedere so I can mount my power brake booster on it.
Anyway, hope this helps the OP out, sorry to muck up your thread. Thanks for your service.