my friend...impedance and resistance are 2 different things. you cannot wire in resistors to change impedance. basically, impedance is when a circuit has resistance and reactance (a moving coil) involved in the equation. an 8ohm speaker is not always 8 ohms throughout its travel and different power levels. just replace all the components in the system. most of the older factory stuff is garbage anywway. you would probably overheat any resistor you would put in there anyway.