There was no such thing as an automatic shifter column in 1950 trucks- - - -I believe the first Chevy truck with an automatic was 1954, which would have been a Hydra-Matic. There was no "park" position, and N-D-L-R positions on the quadrant. "Park" was accomplished by selecting Reverse after shutting the engine down. A mechanical lock on the output shaft engaged once the transmission pump pressure was no longer present. Someone has probably used one of the two 3 speed manual transmission bellcranks to operate the TH 350 shift linkage.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!