When I updated mine I had to use a spacer at the rear backing plate to align the drum to the shoes on the Bendix type brakes. You first remove the rivets holding the early backing plate then figure the thickness of spacer needed and use grade 8 bolts to put the new backing plates on the early rear end. You have to take off the rear end cover to take out the "c" clips to remove the axles since the backing plates have to go behind the axle flange. It takes a while and a little bit of ingenuity, but the result is worth the trouble.