HP 340 manifolds are the choice. What number head do you have on now and which heads are you going with?[/QUOT not sure on head numbers been freshened many years ago. They are not on motor yet,. in my attic been planned so I think comp be ok . I have a set came off a small block many years ago have casting # 2893453 can't remember if came off 318 or ? The original manifolds still on two barrel 318 very hi up on valve cover edge but really small ports