First, congrats for owning a 54 3100. I wish I did. 😎. Since you know the trucks history and that it was indeed running when parked gives you an advantage. There’s no reason to think anything happened to it while parked, is there? Have you removed the valve cover and the dist cap and cranked it with the starter and watched the valves going up and down, and the rotor spinning? Just to be sure all that is working as it should. Could be worthwhile...
It’s probably something really simple. Good luck.
