The basic box was the same from '54-'87. There are differences between the '54/'55 1st and the later trucks on the bedsides, and there also also differences in the bed floor and mountings on the different chassis styles. Mar-K has a breakdown on the differences from year to year.
It should also be noted that the longer beds differed fromthe short beds in number of cross supports and number of boards.


Bill Burmeister