Need help to get truck started

[Lobo'74]

Truck turns over but won't start. Usually when it does this the starter module in the HEI is bad. Took it out and over to Advance Auto. Sure enough, its bad. Replaced it with a new AC/Delco ignition module. Still won't start. It ocassionally catches and runs very rough for about 15 seconds, then quits again.

Since the ignition module burns out about 3 times a year I thought the problem had to be with voltage in or a bad ground. Voltage in is from a switched spade on the fuse block that goes to the HEI only. Pulls the same as the electrical system puts out, 12+VDC. The ground checks out fine. The entire metal body of the distributor shows a good ground. The center sapde on the edge of the coil (C- GND B+) shows a good ground.

I am clueless as to why this 1979 350 in my '67 eats the ignition modules, and am clueless as to why it won't start now.

I sure could use some good ideas here . . .