Would I need to get larger valves and new valvetrain springs if I had high compression pistons? Would not getting these effect the car negatively? Would I absolutely need them?
how much power are you trying to get out of the motor?
getting higher compression pistons will give you more power even if you keep the head stock. Being an NA valves will definitely give you more power, but for the cost you might as well buy used GTE pluming and electronics and get what you 'want'.