Those regulators are adjustable (13.6-14.2 VDC)is the range with engine 1500-1800 RPM lights on.
If yours has a cover that's riveted on, get one at a salvage yard (Delco)that has screws.
Also; Check the voltage at the coil. Range there is: (6.8-7.2) when running 1500 with battery voltage at 14 +/- etc.
Good luck, John M, #3370....
