Need advice on my 318

Picking up my 318 on Wednesday...it is already partially torn down. My goal is to get some extra horsepower out of it for a little money as possible.

I'd already planned on a rebuild kit for it, but while it's torn down I was thinking it might be a good idea to give it new pistons to improve the CR, and a new cam/timing chain set.

Assuming I use Keith Black domed pistons, and with the new cam (but not a new intake, headers, or carb), how much of a increase in HP can I expect?

Or would it be better to rebuild it to factory specs with a new cam and replace the intake and carb? Or machine work on the heads even? I'm ok with milling the head as long as I don't have to shave the intake as well.

In other words, of the following items, what should I go with to get to around 275-300hp?

Pistons
Cam
Intake
Carb
Head porting/bigger valves

If a new cam is definitely in the equation, what cam should I go with? I want the car to be a bit aggressive, but nothing too crazy.