Hi Kris
Meant to respond to you first comment on heaters for HUPs but forgot, I have often kidded that HUP in fact all CMPs have Air Conditioners that work great In Winter and Heaters that work best In summer.
But kidding aside take a look at the Special Cold Weather Equipment supplement that came with the manuals in my HUP some 30+ years ago, unfortunately none of this equipment was fitted to my HUP. It does give a very good amount of detail about the equipment.
Follow this link to the entire manual
http://canadianmilitarypattern.com/S...0Equipment.htm . You will note that much of the heater equipment is basic Chevrolet of the period.
Cheers Phil