You need to get a better understanding about how these trucks are wired.
Do you have a copy of the Factory Assembly Manual and the Chevrolet Truck Shop Manual?
A lot of your questions will be answered there.
The rest of your questions can be answered by the electrical gurus on this site.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission