The Stovebolt Site Forums The Shop Area Engine Shop 1955 truck 1/2 ton 4 speed automaiic tranny hunting info?

I have a basket case! I have a truck that someone installed a three speed manual with an overdrive. They cut the floorboard and put a crappy homemade shifter; but it gets better. They removed the shifter in the column. Then when you look at the steering box they cut the shaft going into the automatic shifting controller unit, with a torch. My question is how can I tell which transmission the truck had; and is it rare to have one with a 4 speed automatic ? If so where do I find one and what would the GM numbers be? Thanks for your help