winter tires mismatching

hey guys

i need ONE new winter tire for the wifes car
she hit something with it and the tire is beyond repair

the tires she has now are weathermaster ST2, and of course they dont make them anymore

now, i really only need one, all the rest have plenty of thread left
BUT the car is an AWD charger

can i put 2 new ones on and 2 older ones?

obviously the thread pattern will differ between the two, but the advertised size will be the same (225/60-18)