Dash control knob for Columbia rear end location, Zephyr 1938

[Beltfed]

Starting to work on the rear end among other things. I have pulled the vacuum control from the steering column to clean up and repair. It doesn't have the mech. cable attached, nor is there anything on the dash. Can someone tell me where the engagement knob is located on the dash and where the cable goes through the firewall? The bracket that secures the cable housing at the control is broken off. I assume the control looks somewhat like a choke cable. The PO removed the vacuum hose from the intake to the control but left the vacuum inlet open. The spring loaded 5/8" ball that blocks the inlet port now looks like a small cannon ball and will not seal the port. Oh boy, something else to fix! Thanks