I was just looking at one I have today. It's off an A body, thinking a '75 Dart but I can find out for sure exactly what it came off of. I can go measure it tomorrow if you still need numbers. I got it because it was small and might work with the dual masters which I think it would.

Also Rich Ehrenberg had some of the Mopar offset mount adapters for shifting brake master to side about 1". Don't think he has any more of them but not a hard item to fab up with a little head scratching.