Butler Performance Inc. - Doug's ROUND-PORT Headers
Identifying headers can be an issue. Here is info to help get the correct headers for your application. The d-port head looks like a set of "D"'s mirroring each other, in other words back to back. The round port actually looks like a sideways "D" that is pointing upwards. This is not a "D-Port" head but a round port instead. Doug's Round Port Headers fit both cast iron Round-Port and Edelbrock Round-Ports heads.