The filter was actually a Regular Production Option installed at the factory.
HOWEVER, it could be purchased as a GM part by the dealer or the owner. Other brands of by-pass oil filters were also readily available (Fram, Western Auto, Sears, J C Whitney, etc) - these could be bought and installed by the dealer or owner or auto repair shop.
If you buy a used filter and need lines, buy the longest lines available in set from many vendors: Jim Carter, Classic Parts (Trucks), Chevs of the 40s, etc. Some vendors sell lines that are not quite long enough for some of the by-pass filters.
