GM-GMC: dieseling, dieseling, torque converter

Question
I have a 1982 chevy 1/2 ton pickup with a 305 in it . I have been having problems with it "dieseling" ( when i shut it off the engine   continues to fire)The timings is right , i've changed plugs and wires,and i was told it was the carb so i put a new one on , but the problem still persists.If you know what it could be and how i could fix it I would greatly appretiate it.
          Landon

Answer
There should be a solenoid on the carburetor that is powered on when the engine is running and that holds the engine at proper idle speed.  When the engine is switched off, the solenoid allows the carburetor throttle to completely close (or very nearly close) and the engine should stop running.

Carbon in the cylinders can also cause hot spots that will make the engine run after it is shut off.  Unleaded fuel deposits cause these hot spots and diassembly is about the only way to remove them.

You can also leave the transmission in "Drive" if it is automatic.  The additional load from the torque converter may help the engine stop without running on.