heater assembly dilemma

[traie8]

Here's one I can't figure out (see pic). This is (or what is left of) my AC / heater assembly. My 72 C-10 was once equipped with factory air, but previous owners modified it to the point that I don't know where to start. I would like to return it eventually to the original factory air, but that will take mooey $$$$$. So, my questions are 1) is there any way I can convert this into just heat by switching the AC assembly to just a heater only assembly and also changing the underdash box and the heater / AC controls switches on the dash? OR 2) can I somehow get the heat to work without the air with this current setup? I've looked at the original schematics, but it just gives me a HEADACHE!!! 3) I've never seen this before...how can the heater hoses be where they are now (see pic)????? Thanks for any help that you all might be able to offer.