"Brother Maynard, consult the book of armaments"

Mopar Chassis Manual, page 169 ..

And the lord spaketh :

"A pinion snubber should be used on 4-speed manual cars (poor devils). Automatic cars don't necessarily require one."

... The adjustable snubber is also helpful on manual transmissions because it enables you to set the clearance of 0 to 1/2". Any pinion snubber used with the manual transmission cars has to be very strong or it will bend and no longer function properly. If the pinion snubber is preloaded against the floor, the car will tend to hop, jump, or porpoise.

The pinion snubber tends to pound the floor very hard. Spreading the load out by adding a plate to the floor and running a brace from the rollcage to the backside of the plate helps keep deflection to a minimum".