If a 1937 GMC uses the same setup as Chev,and I think they do, it will use a carbon throwout bearing.
A carbon bearing can wear the carbon out but if you are experiencing shaking I would suspect some other problem like a broken retracting spring on one of the pressure plate levers.
The bellhousing pivot position for the clutch fork changed in 1938, so if you are changing the whole assembly over to a 1938 design the bellhousing would also need changing.
There is a ball bearing conversion for just the carbon throwout bearing.
Gary Wallace and others sell this conversion.