Have you tried different choke settings, other then full open or closed. You control that cause it is manual, happens to be my preference also. Are you saying at a fixed RPM it is running ruff as if missing or you are blipping the throttle to keep the motor from stalling?

Has this truck been sitting not driven before you got it? The plugs changed were they black as if running rich, what do they look like now ? How many miles have you put on it since you bought it, few or a couple of hundred? Maybe it just needs to be driven. Could run some Marvel Mystery oil down the throat of the carb to clean up the heads, valve guides and seats. These are just some things to consider.

When it is up to temp and all is well it could indicate the need to be driven, take it on the hi way run it 60 or so for 10-20 miles. Cars as well as any machine needs to be run, exercised to keep them running well.

I am wondering what you are trying to say here and what makes you think this ; "Maybe improper voltage to the distributor? I know it needs done as its not putting out what it should"

What kind of system, point, hei, msd type?