Welcome to the site...There's lots of information here which will help answer your questions. Details on the 9" units are easy to find if you use the site's ADVANCED SEARCH feature. Type in 9" rear and you'll get started. Don't forget to also select the Archives when you use the Search feature...Here's a link to your other post which was moved to a more appropriate area of the site: http://www.hipomustang.com/hpmx/topic.asp?TOPIC_ID=6604