Correct SB on the 65-72 disks small bolt pattern....as you mention the 9" issues.....so did the Mustangs 64-66 with their 6 cylinder junk axles breaking even with a 6 in them.
Some early a bodies had Kelsey Hayes four piston caliper disc brakes which is small bolt pattern ...hard-to-find Sent from my iPhone using H.A.M.B.
Indeed, the 73-76 disc A setup Mopar guys would damn near get into fights over - not so much anymore since repop spindles take Volare stuff.