OK, I checked it officially. Napa part for the 160 degree is 91 and the 180 degree is part number 191. There is a 170, but I forgot the number. If you go in to napa, they have a book with pictures of the thermostats, and find the number 91 and 191 and they will have the other number listed there with it. The clue is the 2.5 inch diameter...it is the only set of therms with that diameter in the book. It was an exact match for mine...
http://www.napaonline.com/cgi-bin/nc...age.d2w/report
5 bucks....man that was a long day last week looking to only spend 5 bucks!