[west coast]

If you call it a cold air kit it would not be legal that implies you are getting air from outside the car. that would be like letting everybody putting hood scope on. In the case you are talking about on a 5.0 Mustang you pull air from the same spot as a stock mustang in the right front fender. if nothing can change then you would not be able to change the mass air meter or take the resonator out of the air box. All other carb cars don't have to run 100% stock stuff above the carb if so no drop bases and have the stock lid on them. I was told you anything past the throttle body was ok as long as you were getting air from the stock spot.