Thermostat housing...

That would be a good choice......but dammit. 34 bucks? For a thermostat housin?
The two Motorad ones on RA look pretty good, and under $10... haven't tried one, but they look to have a nice thick flange, unlike some of the chintzy stamped ones I've seen.
1976 DODGE MONACO 7.2L 440cid V8 Thermostat Housing / Water Outlet | RockAuto