Hot Rod,
The meter isn't necessary, just more positive than a "feel". The .018 gap is fine. Did you take the distributor out for the points change and maybe not re-time the engine with a light. Vacuum line is on nice and tight and the advance plate moves freely by hand? Would it run if the primary lead wire and key wire were reversed? Plug wires in proper firing order? I am just stabbing in the dark here, but If you worked on the ignition system, and the truck didn't exhibit any of these symptoms before, I would focus on what was done. You didn't mention plug wires and plugs.
If a engine falters under heavy throttle or load, sometimes it is a weak ignition that can't fire the fuel mixture under that load. If you can put a timing light on it, make sure you have vacuum AND mechanical advance.
Stuart
