I recently purchase a 1967 chevelle SS 396. 325hp, headers, flow masters, edlebrock performer manifold, edlebrock 600 cfm carb, mild cam. I would like a few more cheap horses.  Would a 750cfm carb be worth the money?  Also need to know at what rpm's to shift a big block 396 when racing.  I'm not a serious racer just for fun.
Thanks
the new guy  

What heads are on it and what are the cam specs?  

The engine is a 69 model.  Guessing heads are stock, can hear the cam, and my hearing isn't great ha.   I'm just out to have fun  

If it's a 325 HP motor, it's got oval port heads.

The carb isn't gonna make that much of a difference. With the way the motor is now, you're cheapest and quickest horsepower gain is gonna be bolting on a set of longer ratio roller rocker arms. This will make the motor act like it's got a bigger cam. I'd also upgrade the valvesprings and pushrods to handle the extra lift.

Another good, quick, and relatively cheap upgrade would be an aftermarket ignition system.