wanted 4bbl carb and intake

Install a factory 273 cast-iron intake like yellow68runner suggested. A good reason: hood clearance. Look at yours now with the setup you have, then consider that an aftermarket intake will ride higher, making it necessary to add a low-profile air cleaner and defeating your goal of the stock look. The small 273 runners will match up perfectly with your 318 heads and will give good low-end torque. The four-barrel should yield HUGE improvement, relatively speaking. One problem with the cast intake: you'll need a small Carter AFB as used on the 273, or you could modify the top to accept an Edelbrock carb (the one in yellow68runner's photo has been modified.) Go with the 500 CFM for better bottom end throttle response, since you might not be doing much drag racing. Also, better gas mileage with the 500. Good luck...NICE CAR!