Thermostat housing seeping...

Sometimes rust will erode the factory aluminum ones beyond any ability to seal.

There are inexpensive epoxy products made to fix corroded aluminum seal areas. It works like JB Weld, but it's made to correct aluminum water and oil seals specifically. I think JB Weld may actually be the manufacturer. I've seen it used on really old engines with rare parts and it does a good job.

Although I'm sure that Napa has a replacement housing for cheap that will do the trick. If your intake is a little pitted, silicone sealant with the gasket may be necessary on that end, with a new housing. I'm betting that just replacing your housing with another cast aluminum one will do what you need it to do. Make sure it's been milled on the bottom, though. Some of the cheap Chinese ones are warpy, right out of the box. If it looks like cast aluminum with no milling, you could give it a quick file to true it.