Here's an update and additional questions...

Most of the ignition system (coil, module, pickup, cap, rotor, wires, plugs) has been replaced. A local tech told me it was likely the mixer - I replaced that - still having the problem.

Last night I was here late - quiet so I could hear things. I noticed that as soon as I turned on the key - I could hear a hiss. I found it was coming from the gas line going into the mixer. The truck finally has completely stopped running and hasn't ran for more than a week now. I turned the gas off and bled all of the gas out of the line. Then I just cracked the valve on the tank - truck started and ran like a champ. After the truck warmed up, I opened the valve just to see what would happen - truck ran fine - no issues. I shut it off - it started right back up.

The truck has an Impco CS4-30772-004 regulator on it. The regulator has a device attached that has a two wire harness and vacuum line attached. I'm sort of thinking this a some sort of fuel trim???

Since after it warmed up, it ran fine, do you think it's the regulator? It doesn't really make sense to me that it would be bad since it's just a diaphragm it should either work or it shouldn't, right??? If my assumptions are correct that the attached "valve" is a "trim" device I'm leaning in that direction as the culprit.

This is all sort of beginning to make a little sense - too much fuel fouls a plug - get a miss that seems to be intermittent - replacing the plugs seems to help. But as I've said all along that was just masking the real problem...maybe???

Any help would be greatly appreciated since none of the local techs seem to be able to figure this out.

Thanks!