Differences in A Body brake systems

Thanks Larry / Jarvitron - I appreciate the info.

Oz Mopars were 4.5 bolt pattern in 1972, which is part of the reason for me asking - trying to work out what was different between ours and yours .

Maybe others can help out with the question.... 72 vs 74?
Yes, as mentioned, everything is different between the '72 and older KH 4 piston caliper brakes and the '73-6 single piston brakes. They don't share any common parts.