Get some plastic plugs for that evaporator. Someone might want it. It might be easier to find a non-AC control assembly and attach a cable control valve under the hood. The trick is to have modulation - ability to control the heat proportionally.
Are these 2 pipes the vac feed from the amplifier to A/C & heater switch, and the vac feed to the Inline heater valve? We are thinking of trying a vac feed direct, is the upper pipe the feed to the control switch?
Yes, but I'm not sure which is which. The manifold source is connected to the vac amplifier if I remember correctly. The heat valves use vacuum to close, so without vacuum in the summer, you'll roast.