revted47,
Any change in dwell would mean a change in point gap. The only way point gap could change is if they were loose on the breaker plate and this would be a one time deal...and obvious. This is a toughie. Does the starter turn the engine over briskly when the truck is warm? When you replaced the coil, the new one was a 6 volt unit and is wired + to key and - to distributor.
The only component in the ignition system that is heat sensitive is the coil. Everything you are describing screams carburetion, not ignition.
Did the truck do this before all the tune-up work was done? When you replaced the plug wires, did you also replace the coil wire?
Stuart
