Hen's teeth are non-existent.
53-54 Hydra-Matic transmissions (enclosed driveshaft) are almost as scarce/rare. Those would be the easiest bolt-ins, but you would need a lot of original H-M truck parts to get them to work.
The 55-59 Hydra-Matics might also be a relatively easy bolt-in, with an open driveshaft and open rear end.
Powerglides would be more common; and, more modern transmissions would most likely be the easiest to find.
I think that two sets of 53-55 H-M parts were listed in trucks/parts over the last year.
