Did you replace the timing chain and gears when you installed the cam? You can check chain slop by removing the distributor cap, turning your engine to #1 TDC, and put a breaker bar on the balancer bolt. Rotate the engine clockwise until you see the rotor just begin to move, and measure the distance off the TDC mark. Do the same thing counterclockwise. The rotor should begin to move almost immediately, after no more than a couple of degrees of rotation. If there is excessive movement, either your timing chain and gears are worn out or your distributor has excessive endplay.

You can get distributor shim kits to adjust the endplay, but a replacement rebuilt distributor might be more economical than resolving bad bushings and a worn shaft.

The factory 4 bbl intake and carb should be fine, if the carb is set up for a 350.