Not to take you off in another direction, but, in 1969 Bud Moore had a port problem with the 351 Cleveland motor. The exhaust port had a terrible path even though it was very large. His solution was to mill a rectangular chunk off the entire length of the head down to the bottom of the port and replace it with an aluminum bar with his own high port design. As I recall it was held in place with head bolts.I dont know if it got into the water jacket but you might be able to furnace braze a steel piece to the CI head. He got away with it by calling it part of the header.
