Heat only controls (what cable does what?)

[sventinker]

In my 70 no a/c c10 my father in law added the factory style a/c heat controls and none of the cables line up with the new control. So I want to learn what the cables do so I can figure out how to rig it for heat and or defrost this winter. Would a heat only truck have 2 or three cables? would it have a shut off valve in the line feeding the heater core? Is my stock fan motor 1 speed? or does it vary based on resistors? The fan control I have now has multiple positions.

I know its a lot of questions but I don't know anyone with one of these trucks I hope you guys can help thanks.