No Mounts anymore?

I have a few sets of 73-up B body BB brackets. They won't fit a 73-up A body V8 K-frame without relocating the towers on the frame.
I always thought they were the same. I really lucked putting the brackets on my spool mount BB A-body K frame as I had no issues at all. I either got the right mounts or someone already made the adjustment on frame. I will have see what #s are on the mounts.