My 59 model 3800 1-ton had a SM-420 with a trans-mounted parking brake, a big drum on the output shaft with a brake band wrapped around it and a lever through the floor to apply it. That was pretty much standard equipment for anything 1-ton or bigger, and I believe the 3/4 ton trucks also had that parking brake setup. There should be plenty of them out there somewhere.
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!