In a previous post you say your start switch doesn't have a side terminal ("...currently the starter on the truck has no side terminal."), now you say it has one that is closed all the time. It makes it hard to help you.

The wiring diagram in the shop manual is for an 8 cylinder truck with a key start switch. The resistor bypass system on them is different than a bypass system on a 6. On the V8s there is an ignition 1 terminal and an ignition 2 terminal. When the key is turned to 'start', 12V is sent directly to the coil. When the key is released to 'on' 12V is sent to the ballast resistor which reduces the power to the coil.

Since you say your truck has a key start position and the purple wire, I'm guessing your truck was a V8 truck from the factory. You can't use the switch bypass system from the solenoid starter of the V8 on the mechanically operated starter of the 6.

You need a starter switch like this on your starter wired as stated above.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.