LAPD and CHP had a lot of pull back in the day but I have to believe this is an urban legend on this cam grind story. You state to "keep them going" at 140, if the car can get to 140 it will stay there. I do know that by the mid 70's the police package 440 had lost a lot of its balls.

If you look at the late 60's parts catalogs these two agencies had their own part numbers for suspension and brakes, maybe other parts. If there is a cam listing for them then this legend then becomes fact.