Without more details here is what I got for you:
Part #
OEM#
Teeth
Ratio
C8.25-271 3837580
46-17
2.71
C8.25-294 3837581
47-16
2.94
C8.25-321 3837582
45-14
3.21
C8.25-355 3838583
39-11
3.55
C8.25-390 3837584
39-10
3.90
If they are readable look at the serial number of the car and the numbers on the door. A lot of times the numbers on the door jam will give you that info in a code book.