Put 12-16 degrees initial lead in at the crank. Curve the distributor to add additional centrifugal lead to total 34, all in by 2800.

Dieseling was such a problem with the hot-running, low-compression motors of the early 70's that the OEM's installed dashpots (electric solenoids) on the side of the carbs that, when the key was turned off, the solenoid relaxed and completely closed the throttle blades. When you turned the key back on to start the motor, the solenoid energized and cracked the throttle blades open to the idle position. If the motor can't get fuel/air, it can't diesel.