My old leaky POS spin on adapter of unknown make used the Fram PH3600. Now I've got the Mocal adapter and I'm using a Purolator Pure One PL20195, or you could use the regular Purolator premium which is just L20195. They claim the Mocal adapter can use any Ford filter from the late 50's to the mid 90's I believe, thread size and sealing gasket diameter are all the same. The differences lie in canister length and overall diameter, so you've got lots to choose from. However I found most of the V8 spec filters were a little to large, I wanted something that was basically the same diameter as the adapter itself. I think the part # I used was spec for an 88 Escort 1.9 liter four, and it fits perfectly. Same diameter as the adapter end plate.