With the shipment of parts in from MidWest yesterday (though, somewhat unsurprisingly, I need to make another already ) I can now replace the thermostat that I think has been a bit flakey (and definitely looks like it's been in there for a while).
The original bolts don't look bad and I could easily clean them up- but I generally replace most original hardware with stainless when I can, and they're fairly standard bolts. Given the original ones are also steel bolts I wouldn't expect that going to stainless would cause any issues, but since I've not really replaced much of anything going into the engine yet I figured it wouldn't hurt to ask...