Don't become all steamed up, if your thermostat is not proving reliable, it would be better if you replaced it before the engine overheats once too many times! A new thermostat is a lot less than removing cylinder heads, skimming them and then replacing with new gaskets! But if you are already committed to a rebuild or restoration, browse the online 'parts list' fiche for your Goldwing, and access all the parts availability. It is extensive!
Note: this part is superseded by 37760MB9000.