It worked!
Today's two questions:
1: How do I test the vacuum tank?
2: I've looked at the shop manual, but it's just not making sense: how do I drain the coolant? Shop manual says there are 3 drain cocks - one on the radiator lower tank and two on the engine block - but when I poke my nose under the front all I see is a mystery-maze of metal. I see nothing I can identify as a 'lower tank,' - the radiator lower hose seems to go to the engine - and I'm not sure where on the engine to look, either. There's a round hole (6" or so) in one of the metal plates under the car, through which I can see two bolts, but those don't look like 'drain cocks' to me.