My first car had wooden floorboards and pretty sure had wood supports in the seats, both in the cabin and in the rumble seat.   1931 Model A Ford.

Had a 36HP VW had 8 pieces of wood in the engine.   One Inside each pushrod.  Supposedly at certain rpms the oil delivered thru the push rods to the rocker arms would surge and not deliver.   By making the size of the delivery space smaller no more problem😃.   The wood only reduced the delivery space, not sealing it off.    

Ron