I believe you all are correct and it is a powerglide trans cooler. See link as there are two threaded connections on the backside which I'm sure were an inlet/outlet.
The only strange thing is this is a non-pressure '53 235, so perhaps it was mated to a powerglide later on in life. Expect to see this part on e-bay in the not so distant future.
Thanks as always! Stovebolters rock!
Big Tee
trans cooler other side
