Disc brake identification

Well, A bodies, and B bodies, both used those slider type calipers, but with the differences in the rubber flex hose location on the caliper.
From what i can see in your picture, you most likely do have a 73-76 A body, disc brake set up.
Another difference is also in the spindles, between the two.
More pictures would be of help.
Those numbers on the calipers are pretty much meaningless to you and me, the common enthusiast.
They must have meant something at the foundry, manufacturing level, but nothing to do with identifying them, 40 + years later.
You gotta know what your looking at, in this case.