Probably a dumb question but are you sure the hi-low switch is in the dash? Would make more sense for the dash switch to be pto or something else.

Stuff I’m gonna work on, I swear
1963 C30 flatbed
1961 Apache 30 (parts, no title)
1960 GMC Big Bolt

Don't tweet, face, Google, or link. Just hanging in as long as I can...