General thinking is to make the car run as well as it possibly can in stock form before you start tinkering. Carbs alone won't get you better performance (unless you're swapping the later EPA 'flattop' ones for the earlier round-tops). Neither, necessarily, will a different head. The L24 was a magnificent motor in its own right and doesn't need a lot of messing with once you really get it dialed in. As far as the auto, Datsun's auto trannies are about as bulletproof as the engines. Enjoy!