Yes, auto was available. As Joker says, hard to find. Don't know if parts available to rebuild and not modern design. Also needs automatic column shifter and linkage from a donor. Don't think it would fit the 350 motor. I would not go down that road.
Simplest swap is 350/350, adjustable cross member and Lokar shifter. Several options here so far. Think it over. Others may give their opinions as to what is best. May need a radiator change. Are you on a tight budget? What is your experience with truck mechanical. Do you have the equipment to do this or is someone going to do it for you/help you?
I guess if you left the 6 cyl in, the scrap yard auto would bolt on.
From the web:
GM's four-speed Hydra-Matic. It was available with the six and the V-8. The truck Hydra-Matic was the same unit used by Cadillac and Oldsmobile.
