I have drawn a very simple ignition diagram to help you understand what is happening in your ignition system. As you stated that the truck runs in the start position. This means that the ignition system is working ok, so the problem has to be in the ignition switch or the resistance wire to the coil. (It Can’t Be Anything Else) as you can see by the diagram the only difference between run and start is the resistance wire. You stated that you put in a new ignition switch, so that eliminates the switch. This only leaves the resistance wire as the culprit. You stated that you ran a jumper from the battery straight to the coil and it still didn’t run. You must have mistakenly put the jumper on wrong because this is an impossibility. If it runs in the start position then it would have to run with the coil connected directly to 12 volts. I hope this helps. Good luck solving your problem. I spent nearly 50 years in the automotive electrical industry and believe me I have seen some weird and perplexing problems.