kwf: I can confirm what Tony said about aftermarket equipment. I started selling dump bodies in 1967 but absolutely nothing changed in those 5 prior years. As a body manufacturere we had our equipment dealers/installers (called mounting services)who sold the bodies to truck dealers locally or nationally if it was to a larger fleet accout.
None of the chassis manufacturers built equipment tho' at times some incidental pieces were offered to the ordering truck dealers. This was installed in the detroit area or wherever the chassis was built by outside companies and billed to the chassis makers who passed it on to their local truck dealers. It is still being done in a somewhat modified manner and certainly on a larger market basis. Those flatbed and stake bodies you see from time to time were built to be sold thru the chassis builders as a contract item and were never built by the truck factory, niether F^*d or Chebbie.

Once you understand it it is a simple process.

1953 Chevy 5-window 3100
In the Stovebolt Gallery
More pix on Picturetrail

Dave
Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain