hi,,this was a disc brake mc,,.i think it all boils down to stopping a imperial safely and reliably,,the old design mc s were not that good and the power brake boosters of that period left a lot to be desired,,..the brake drums and shoe design is very very good with a late model duel mc that can put more pressure to the slaves evenly..and if you blow a line on ether end of car your still going to stop with the other end..and it saves a lot of shoe leather!!!,,thats the beauty of the duel mc..orignalitly only goes so far when driving these monisters in city traffic,,id rather stop ,,strait ,no pulling to one side or whatever...rick