I'm sure that you have been given every suggestion under the sun. I'd probably use a intake manifold that has ports close to size of the 318's cylinder heads. Carburetor, the smaller carbs will give you the best throttle response and low to midrange torque. A lot of guys are going to suggest a bigger carburetor but for what it sounds like your looking at doing a 500 cfm is plenty. If you upgrade to better heads, cam, then yes the bigger carburetor will be needed. I think that a 500 cfm carburetor, good intake manifold, 4 hole 1/2" carb spacer, 340 cam and dual exhaust will make you a fun ride. This probably already has been said, I didn't feel like reading the whole thing again. Happy hot rodding.