If you go back to the late sixties, early seventies chevy and ford had some factory automatics. One thing to remember is it is not a big deal to put one in the truck of choice. Tranny w/ flexplate and torque converter, driveline, mounts, tranny cooler and it's done.

according to parts books i have chevy - gmc and dodge trucks came out with automatics in 1954.ford came out with thiers in 1955.these were a very limited production .