47-55.1 51 Chevy 3100 w/ 235 - MIssing/running rough

[duramaxguy]

My '51 has always been the smoothest running vehicle I have. Fires right up and runs smooth at all RPMs.

Coming up the hill the other day, it started surging and coughing (not backfiring) and lost most of its power under a load.

My initial thought was a fuel blockage of some type. I replaced the fuel filter, fuel pump, and have rebuilt the Rochester B carb. No effect.

Now I am suspecting an ignition or mechanical problem of some type. All plug wires are secured and the cap/rotor are in good condition.

Suggestions of troubleshooting steps?

Thanks in advance.