I have an original fram external filter cannister on my 54 235, and it works rather well. I replaced the hoses to in and cleaned it out/repainted and reinstalled. Oil filter cannister is a cylinder shape that surrounds a central post. oil comes into the assembly from outside the filter and is pull;ed through the filter and sucked back into the engine through a smallish hole midway up the center post. If allis clean, it works pretty well. Didn't materially affect my oil pressure with or without filter in the cannister.
