A Truck-O-Matic would be cool to have. It’s essentially the M6 transmission behind a Fluid Drive coupler. The same setup that Chrysler, DeSoto, and Dodge cars used under different names. Prestomatic, Tip-Toe Shift, Gyromatic. It may have been a 1 year only in the trucks. Shortly after that the automatics came out. As you may have read, it’s a 4 speed trans with semi-automatic shifts between 1st/2nd, or 3rd/4th. You have to manually shift between the low and high range gears. For most driving around you could put it into high range and drive it like an automatic vehicle. Only need the clutch to get into gear initially, or to shift ranges or directions.
If you could get the engine running you could probably just swap in a standard 3 speed behind the Fluid Drive. That was also an option in the trucks. Or, sometimes you can come across a complete drive train and swap out the engine trans combo. As you can guess, the bell housing and everything would have to be swapped out to remove the FD. The axle can remain as is unless you want different gearing. You can always find a 3.90 or 3.73 diff out of a car from that era that will swap right into the axle housing.