It's called "static timing", done with the engine stopped, and the flywheel ball aligned with the pointer. Either put the truck in high gear, and carefully roll it forward until the ball and pointer comes together, or try turning the engine with the fan if the belt is tight enough. Be sure you're on the compression stroke of #1 cylinder, by either having only the #1 plug installed, or watching the valve action. Once you're sure you're on the #1 compression stroke and the ball/pointer aligns, remove the cap so you can see the points, turn the distributor housing clockwise until they close, and turn back counterclockwise until they just barely open. A test light attached from the coil (-) terminal to ground helps find the exact break point. With the ignition turned on, the light will go out with the points closed, and come on the instant the points break.
With the engine static timed, it will start, and be within a couple of degrees of the final timing point. While you've got the cap off, compare the rotor position to the corresponding plug wire terminal in the cap, and install the #1 wire to the cap tower nearest the rotor tip.
Jerry
Edit: By "cam" I mean the distributor cam, the thing that makes the points open & close. Nearly 50 years of tinkering with these things makes me think everybody jumps to the same conclusions I do when describing a procedure! Sorry!
Jerry
