Jesse,
There was a change in brake parts between 1957 and 1958 (per the parts books)...what changed I don't know as I've never seen the two side by side to compare.
If you have the GM rear it's rated at 15k than the info I provided in the earlier post will be incorrect.
Per my 1963 parts books the 15k rear used from 1958 thru 1963 is part number 3748514.
Per my 1967 parts books the 15k rear used from 1958 thru 1966 is part number 3877023.
What caused the part number to change I can't answer, but it could have been something as simple as the number of rivets holding the facing to the shoe...
Mike B
