In my opinion the only way a pinion snubber works is it must be adjusted to within 1/4” to 1/2” away from the floor pan. If your front suspension is working properly disregard. The reason why is remember, Mopar leaf spring cars rises in the rear at launch and then settles down. That means the floor pan goes away from the snubber making it useless. Also driving the car around on the street you will feel every bump.
If you use a split mono leaf from Calvert and it is sized correctly to your car's weight, the rear end will remain stationary or even drop slightly as the tires hit the track, but it is the same effect, the snubber would be moving away from the floor pan.