Also, looking under the dash at the heater, I can see corrosion on the control valve, so maybe that's the issue & the core is actually good?
The push button vacuum switch was broken (nipples on the back), so I got a restored one & installed it. On the plug with the vacuum hoses that plugs into the switch, only one hose (red stripe on hose) was cut. I'll take & post a pic of which vacuum pod it went to.