"The seal is a press-fit into the thermostat housing. Great care must be taken to ensure it is not damaged and stays straight while installing. The thermostat has a slight interference fit where it rides against the rubber ID of the seal. The…"

"I've heard these are a Cadilac power seat motor. I don't have confirmation of that though. Mine have been modified to use Lenco actuators with the factory tab mechanism.
 "

"I have a couple, they can be taken apart  cleaned and lubricated, hard part is sliding the armature over the brushes
. Worth a try"

"These are not available new, and used ones pop up occasionally on the usual second hand online markets. There isn't much to these motors; most of the trouble comes down to stuck or dirty brushes or corroded leads. If you can find a local motor shop,…"

"A dissertation by the Late Great C6, Dick Morland:  https://storage.ning.com/topology/rest/1.0/file/get/9468114501?prof...
Note this is in the Files section, amazing what you find when you look. 
 "

"Editor Note:
Take a look at these discussions for more information from Norm:
https://commanderclub.com/forum/topics/discussion-forum/listForCate...
https://commanderclub.com/forum/topics/discussion-forum/listForCate... photo of seal wanted"

"Glad you found a stat. You better check that seal or get one. In this scenereo it is more likely the seal . Good luck."

"140 for open cooling to prevent deposits  160 for closed system. "

"I am going with the missing seal. Lee and John are correct. I got my last ones from Harpurs. They still list them in their catalog. I have an old one for sizing, but no one seems able to duplicate. My old one is not usable but good for…"

"Is the rubber seal in place around the stat perimeter? If not I still havent found a source for the replacement but if it doesn't seal it mimmicks an open stat. Somebody may have a source by now. 
Lee"

"I'm fighting the exact opposite problem on my closed cooled 427 at the moment and have since learned a lot about these and the raw water cooling systems. The only way that a raw water cooled engine can run colder than the thermostat range is by…"