I think you went back 1 or 2 years to far.
Your 66 would have a 3 knob set up for the deluxe heater.
I don't think the 4 knob set up will fit in your truck without major modification.
Maybe you could sell what you have now to finance what you need.
You will need a 3 knob dash set up,the three cables, the deluxe heater box and the deluxe heater core and box.
Then just follow the installation as shown in the factory assembly manual or accessory installation manual.
