Here's a chart from a old post here. Wix filter numbers:
7" tall - 51773
5.1" - 51515
4.3" - 51068
3.8" - 51085
3.4" - 51348
Check out http://www.wixfilters.com/
Good site with an excellent interchange info.
Fram ph16 is the taller filter that doesnt always fit with headers. Ph43 is the shorter one that lets alot of us get away without using a filter adaptor. I have switched to the wix equivalent though. Great filters.