Heater Core

Man, it sounds like a vacuum issue. But I guess it could be a door not opening mechanically. I think the linkage on the right side of the box, about where your left knee would be if you were sitting) is the one that opens and closes between heat to the floor or to the two holes that send it to the defrost. Its right up against the box. Try moving it up and down manually.

I remember pulling mine and I think you're right, I think I only disconnected the vacuum lines from the solenoid above the kick panel.

You might try pulling the glove box and making sure the vacuum lines coming through the firewall are connected.