Pinion Gear Removal – ‘39-53
The ‘39-53 pinion gears were a push or free sliding onto the pinion shaft, but should have no perceptible lash. Even a slight lash will usually result in noisy operation for which the other timing gears are often held responsible. To correct such a condition will require replacing the pinion gear and or pinion shaft. There is no nut holding the gear in place, like there is on ‘54-72 assemblies.
- Vol.2 M&O Guide
Does your motor have this pinion shaft? You can't feel for pinion lash without removing the pushrods and gears and oil pump & everything in there. You'd get an insight into how the motor was built, by time you got clear down to the pinion pool in the gearcase. If so, do so forensically
for record of what-to look-for, or just ride it.