How would you rebuild this 318?

If the OP is happy with the power he makes, then yes nothing needs to be changed combo wise, but since he asking what to change sounds like he's looking for more power. And that's mainly done through cam and or heads, better heads probably be more streetable than larger cam, especially if he's not changing cr and or gears. Something got to change if the goal is more power.
Correct. But how far does he want to go and how much money does he want to spend on a 318? Unless he's going to add a roller cam, some exotic heads, turbo or blower, he's not going to make a huge difference from what he has now. That's why I recommended sticking with what he has.