This may be the window you need:
http://www.trekwood.com/products/506...ack-Frame-8500
Measuring windows is a "tricky venture" and often ends in guessing wrong. Some vendors measure the outside of the window frame, others measure the glass, still others measure the lip of the molding that sits on the trailer framing. So you might guess right, you might guess wrong. It would probably be better to call Trekwood (their info is on the website at the above link) and discuss your needs. Trekwood has one of the most comprehensive inventories of Keystone parts available. Good Luck !!!