Will not start

Does it get fuel? Spark?

Charge the battery completely. Use a starting fluid in the air horn to see if that coaxes it into starting. Loosen the distributor hold down bolt and slowly turn the distributor as a helper cranks it over. If it starts. Fine tune the timing and lock down the distributor.

No. The starter fluid ruled that out. It's either timing or spark. How strong of a spark did it get? Are all 8 cylinders getting the same strength of spark?

Pull #1 plug and rotate the engine until the #1 piston is at the top of its rotation. Look in the plug hole to see. Check the crankshaft dampener. You should see a groove in it. This groove should be aligned with a timing mark. Clean the timing indicator and read the number. What is it? If the truck has a distributor, remove the cap and see what plug wire tower the rotor is pointing at. It should be #1. If not, rotate the engine by hand another 180 degrees until the piston is back up top and check the dampener mark and the rotor. Don't rotate the engine and try to line the rotor up with the wire. Rotate it to bring the piston to what we call top dead center on the compression cycle.