resistor

i have converted to msd 6-tn and muti step retard unit on the car, but i left the factory icm box just upgraded to mopar orange, and a few mins, if msd craps, can drive home, now, i still have the 4 pin in the car, does it have to changed to a 2 pin unit? or can i just leave what i have, like i said just a back up. 1973 dart swinger. ???