If I remember correctly, the filter was a "Option" in `1955, in 1956 they went to a "Full Flow" oil system and the oil filter was in a Canister mounted in the normal small block place. It was quite a juggling act to get the filter, canister ,square o ring and long bolt with a gasket under the bolthead all lined up correctly so it wouldn't leak. My first OSM (oh shit man) moment was when I didn't remove the o ring and just put the new one in and had a tremendous oil leak ( Gusher).when I started it up!! I think I was 16 at the time on my first job after school...