Just clarifying here the truck does not crank or the truck cranks and does not start? Should be the large cable from the battery, and two feed wires on the big post on the starter and the crank signal wire on the little post. The manual I have for your truck shows that as a purple wire. That purple wire runs up the harness through a connector into the cab to the neutral safety switch. (If it is a manual trans it goes to the clutch safety switch.) From there it goes to the ignition switch.