Transmission didn't have a parking pawl back then. The parking brake worked pretty well, it had too!
In car you've never seen one, there's a small brake drum, about 8" in diameter on the back of the trans, the drive shaft bolted up to the back of it.
Oh, another funny thing on these transmissions... you could actually push start the car. The transmissions had a rear pump in them.
Plus there was a safety feature built in that if you moving over 10 mph, it would prevent you from shifting from forward to reverse by accident. Or vice versa.