when i turn off my car it keeps sputtering

Look for a tach/dwell meter at garage sales. Many out there, and of no use on cars 1990+. Same for a timing light. Several things can make it "run on" or "diesel". One is carbon deposits on the head from running too rich at low speeds. Some say an "Italian tune-up" like running full throttle up hills can burn it off. Aren't you near the edge of the Cumberland Plateau for that?

A throttle too far open at idle is another. There were carbs in the late 70's thru 80's with "anti-diesel" solenoids which shut the throttle tightly to stop run on. I think they needed them then because of the emissions controls and settings they added that messed up a smooth idle and required the throttle be more open at idle. Thus, anything you can do to get a better idle and allow you to set the idle throttle more closed will help.