This first link shows the major components of the deluxe or fresh air heater.
http://www.64moneypit.pages.qpg.com/6066chevytrucks/id36.htmlIt requires the large sheet metal box in the engine compartment to mount the heater core and fan motor. The recirculating or economy heater mounts the core and fan motor in the cab, and only the hose nipples and mounting screws show in the engine compartment. I believe the firewall changed in 1963, so any 60-62 heater should be a direct bolt in to your truck. I had a deluxe heater in my truck long ago and didn’t like how much room it took up under the hood, and it always smelled of antifreeze in the cab, even though the core was new and didn't leak. I replaced it with the recirculating heater and it works fine in the sub freezing temperatures we get in the inland Northwest.
The following link shows a beautiful example of a restored economy heater. The defroster part of the ducting is not shown, and is the same on both the deluxe and economy heaters.
http://67-72chevytrucks.com/vboard/showthread.php?t=367522&highlight=economy+heaterI’ve tried several aftermarket street rod heaters and all were worthless heating the cab in winter, unless you live in reasonably warm climate.
Here are a few more related threads:
http://67-72chevytrucks.com/vboard/showthread.php?t=368598http://67-72chevytrucks.com/vboard/showthread.php?t=294960&highlight=economy+heaterhttp://67-72chevytrucks.com/vboard/showthread.php?t=267251&highlight=economy+heater
