whats the deal with mopar thermostat housings?

I thought I had this problem licked with a new t'stat housing (pot metal, not chrome) from Advance Auto, with a new FelPro gasket and Permatex silicone gasket sealant. After 500 miles I began to get a slow antifreeze leak around one of the bolts. What a nuisance.

So, I dropped in 2 GM coolant system sealing tabs and drove the car 20 miles. The leak has stopped- for now.

For anyone wondering if these tabs are harmful to cooling systems- GM installed them at the factory in trucks in the 1990's and required they be used with every antifreeze change. I always used them in a '95 Chevy van and never had a spec of cooling system trouble in 13 years.