The Label Options in Word 2007 (and every other version) contains Avery 8160 and 5160 definitions.
First make sure you have the Label Vendors dropdown set to Avery US Letter.
In the product number list, don't expect to see zeros at the beginning or end of the numbers; they are just 8160 and 5160. Also, recognize that the list is in "alphabetic" order and not in numeric order; in many cases, 4-digit numbers come
after 5-digit numbers, as if the digits were letters.