thermostat replacement

If the bolts are drilled into water, water will climb those threads.
I cant comment from experience about the chromed aftermarket housings.
There have been quite a few times when I replaced a thermostat under the OEM housing, and yes there was a tiny seepage initially under pressure. I ignored it until a day or 2 later. It stopped leaking every time.
Am I saying others are too quick to throw more money at it ? No.
Only saying I'm not as quick to buy another gasket and try again.
Good luck with it.