Mike B,
I found these two pictures. ( Hope the link shows)
Maybe the ones we were thinking of.
My interest in this was to see what the SM420 set up looked like so I can adapt it to the SM465.
The SM465 trans I have uses a cable pulled drum brake on rear of transmission to act as a prop shaft parking brake.
The donor step van had a hand lever like I've seen on fork trucks.

Floor lever would be much better!
[img]
https://flic.kr/s/aHsmRqpGLD[/img]
Pete