[TheWhiteElephant]

The junction at the firewall is the little black plastic block with 2 posts where several wires meet. Sometimes they become dirty or loose, have improper contact and can result in your truck not starting. And as stated above, there should be maybe 2 fusible links at the ends there. My old K5 used to do this to me on occasion.

If you don't know what fusible links are, they are sections of wire that are smaller gauge than the wire they are protecting. They are found at the "ends" of the wires. They burn out when there is an overload of some sort to protect the components. They will not necessarily look damaged because they are made with a softer wire cover that prevents the wire from burning the covering and catching fire. You can tell if they are damaged by wiggling it around. If it feels like something is burned or broke inside, then you need to replace it. If it feels normal and pliable, then it is okay.