The manual for Rick's machine shows lubing the back gears with the plugged hole between the gears on the bench models. On the cabinet under drive models, it shows the ball oiler in the right end of the back gear spindle. There are two separate lubrication charts for the two versions.
The purpose of the hold down plates is to keep the carriage from being lifted off of the bed and V-rail. If the factory didn't install shims there, they must have considered the running clearance as not critical so long as it was a positive number and assumed that the weight of the carriage assembly was sufficient under normal circumstances.