I would imagine for the most part the valves and springs would work, since they seem to be of the same diameter (37mm intake/30mm exhaust) as the Mark VIII/early Cobra castings. i'm pretty sure the cams are interchangable back and forth between them as well....although I'd rather match up the right heads to the right cams for full potential. You do realize you'll need a later model Cobra intake to work with these heads as well, right? The early "twin port" B heads won't work with the '03-'04 Cobra heads.