I've decided to reuse the 186* thermo, but does anybody knnow the PN for the O ring seal? I cant find it anywhere...

It was like a flat o ring originally. I looked everywhere for one, nobody sold it separately. I ended up ordering a whole new thermostat so I could get it, and of course you have to order the whole housing. $40 later I got it, and the gasket included was just like a regular round o ring, not a flat one. So I was unhappy but used it anyways. I suggest looking through the local parts store's o ring assortment and getting one the proper size.

Thanks!! I ended up getting one at Advance auto. They had like 50 of them. FelPro's