Put one new spark plug in #7 cylinder and go drive it real easy at part throttle at or under 2300 RPM for 10 to 15 minutes and then look at that plug, If it is black again lean down the idle air fuel mixture and try again to get it right wrench scope
Make sure the carb is idling on the idle circuits only, not up on the transition circuit tsk scope

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)