Here's some info I dug up(told you I would get back to you, just a little later than most)

A crew cab was aftermarket from the fallowing companies:

Proctor-Keefe body co; INC. Detroit michigan. They did not extend the chassis and did not use a ford door handels or windows for the conversion. It had one door on left side, two on the right. Would look like a hick job nowdays.

Armbruster and Co: INC. fort smith ark. Uses ford doors and has for of them, uses shortned frame. Looks like a quality job.

Crown steel products, N main street, orrville, Ohio

Appears to use 4 ford doors with vent windows still intact on a shortned frame.

How's that for getting back to you? These are not all of the manufactors of bodies in 1960, rather the ones out of an aftermarket catalog from a ford dealership from 1960. -4speed