Obviously, it could be a lack of spark or a lack of fuel delivery. By chance did you happen to notice whether the fuel pump made any sound whatsoever when you first turned on the ignition switch (prior to engaging the starter)?? If you can pull a spark plug, you can determine whether or not you are getting spark. Just remove the easiest to reach plug, connect the plug wire back to the plug... and set it near some grounding metal while you try to crank the truck up. This is where it would be good to have someone help you for a second. If you see a spark... or, you don't see a spark... at least you have made some progress in diagnosing the problem.