My online research so far seems to suggest that when the BBP 8.25 axle replaced the 8.75 in A-bodies axle for the '73 model year, the 10x1.75" brake setup died with it. All listings on Rock Auto and NAPA seem to back this up, that said factory oddities of all kinds likely exist. Honestly, I want the Doc Diff 10.7 disc setup but it's out of stock.