You're right! I just went out and measured them. Great! I forgot to mention that I wanted to get 10" with the 4 1/2" bolt pattern, if I was going to swap. Just to make the bp's the same. This is going to be a limited-use street/strip car, so I really don't care if it has two different patterns, if I already have the 10". This eliminates having to swap the master cylinder, too, since I thought it was a 9" set-up.
I don't want discs' because I want to try these:
http://www.musclecarbrakes.com/stage1.html Years ago, I had semi-metallic shoes on a Challenger, and it stopped better than anything I've driven, before or since. It had 11" drums, but I want to see how these work. I'm not sure, but I think discs' are heavier and they drag some. I'm going to use manual adjusters, also, to keep them from dragging.
Something else: In the 90's a friend and I built a 71 RR for NHRA stock eliminator. When we ordered new front (10") drums, one was 10lbs., the other was 19lbs.! We got another of the 10lb ones! Never had a problem stopping the 3900lb car from 116 mph. It had just regular shoes.
Whaddya think?