The Stovebolt Site Forums The Shop Area The Electrical Bay Backup Light Switch

There was a fed govt required backup sitch on SM420 transmissions in its last year, 1967.

Here is a little write-up of the add-on back-up switch that I think that Bill is referring to.

Here is an installation diagram. (posted by 4-5-6 Chevy Trucks)? Here is the full thread.