what year head the new 1999 head has a small er ex port or P ports are rounder .all the big block big O port and Rec iron heads stock are not round BuT there somewhat square all bout the same size .if you have headers you get the header a hair smaller gaskets for the size of tube on the header and if its round on the header flange then its the gasket you run if square then that the gasket you run any other way it will leak