Sheared thermostat bolts?

You shouldn't need to replace it for the two bolts. First take a torch and heat the areas around the bolts so it gets hot, that will cause the JB weld to break down, so it isn't holding. Then center punch each of the broken bolts, now use a left-hand drill bit to drill straight into the bolt. If you are lucky the heat and drill will be enough to cause it to back out. If not then use a spline style extractor and see if heat, and some penetrant will get them to move. Worst case you would drill out the holes oversized and install Heli-coil inserts to get back to the stock bolt sizes. Just be very careful with the drilling, I would get the two new bolts and the housing and use that to see how deep to drill. You don't want to hit anything important while drilling the bolts out.