Classic/Antique Car Repair: 1970 GMC engine

Question
My truck would only run about 15 minutes, then die.  I would try to restart it but no fire, I'd have to wait an hour or more. I replaced the fuel pump, checked for vacuum in the gas tank, currently don't have a fuel filter.  I replaced the ignition coil today and it ran for 30 minutes now, but still dies. It turns over but no fire for an hour or so.  It's a 350 with HEI distributor.

Answer
Several things come to mind/ I would tie a fuel pump pressure gage into the fuel  line and see what happens to the fuel pressure and flow when the engine dies. Second make sure that there isd the dielectric silicon grease under the ignition module.  The grease is neessary to make a good path for heat to transfer from the module to the distributor body.