Hi,
Either firing order will work. There is a problem with the old firing order. Cylinder 8 fires right after 7 , they are next to each other and cylinder 8 will run lean if you have a open plane manifold. The wilder the cam, the worse it gets,as the overlap for 7 will kill the intake charge for cylinder 8. so it's better in performance applications to use the H.O. firing order.
Perry.
