DONT PANIC!

Right, take a look at the stat - you'll se on the flat edge, a line. Cut along this line, all the way around. You'll remove about 2mm from the diameter of the stat, without affecting it in any other way at all. It will now fit into the housing. A Ford gasket ring is quite thick so you may have trouble gettign the clip in. You can either find a thinner rubber ring, or use gasket sealant suitable for such a job - Loctite Gasket number 2 is what I used.

Edit - just noticed from the pics, that the line is quite clearly visible. Due to the nature of the clip, you dont have to follow the line exactly round, just thats about where you need to cut. It takes about 3 minutes with a Dremel wheel.

Also, it certainly is an 82 deg. stat - take a close look it should have it stamped on it.