You might try contacting Ken Austin at A-dec ( Austin Dental Equipment) in Newburg, Oregon . He had a sideline business supplying multi-cab manifolds for Ford and Lincoln flat head engines, including the flathead Lincoln 337. I bought 3 four- barrel V-12 manifolds from him and they were quality pieces and fit and performed well. I don't know if he's still doing this but it's worth a try. He may even be able to help sourcing the heads. Good luck