My father has a 408 stroker using a 360 block. 360 J heads with 1.94 intakes, 11 to 1 compression, MP .528 mechanical cam, and 1.6 ratio rockers. Pulls very consistent low 11's in a '72 Dart. I know high tens are reachable with better heads but he can't justify spending the money on a bracket car and I agree with him. Sonic check your 318's. One of them may be able to be bored enough for over 400 cubes.