Ya, I don't have a new gasket for the thermostat housing. You think leave the gasket off and just use sealant on that?
I had our mechanic at work teach me how to "tap" out gaskets with a smaller ball pein hammer about 40 years ago. It's gotten me out of a lot of pinches over the years and save a lot of money and time. Year ago you could buy flat sheets of different thickness gasket material, and for different purposes. Some for oil some for water/coolant. I still make a lot when going over a tractor, especially PTO covers, axle housings when installing new brakes, seals, etc. Mainly on cast parts. The one you need would be easy.
Now seems gasket material comes in rolls to conserve storage, I guess. That mechanic also taught me how to make those round rolls flat PDQ. He'd cut a piece of material big enough to make what he wanted, then take a steam iron, spritz some water on the gasket and iron it flat. I keep a scrap piece of 3/4" plywood in the shop for my ironing board, then lay a paper shop towel on top, underneath the gasket material. Works like a charm.
You'll want to tap out the bolt holes first to hold it in place. And in your case, then tap out the port in the head, then the outside. I've got quite a collection of ball pein hammers I've collected over the years, picking up at swap meets, yard sales, thrift stores, etc. the pointier, the better. And numerous rolls of gasket material. For that one, you'd want something coolant resistant. Just takes a little time and patience. If you have a some fuzzies hanging on like in the last picture, I keep several utility knives around. Just rake backwards and they come right off.
