I'm currently rebuilding a 1974 455 that is sitting inside a hearse , the car is a 98 . I put two 72 G heads on it after discovering that there were two different heads when I bought it . But I changed the cam from a racing cam to a crower stage 2 with a .448 .450 lift , after doing so it ran smoother but the valve springs were worn so now I am wondering what valve springs and valve stems to put in to match the cam lift ?