Here is a photo of the recirculating heater in my 54 3100. I just refurbished it. You need to get under the dash and see if there are defroster diffusers. They would be a flat metal duct attached to the slot in your windshield were the air would flow out. The bottom end would have a round opening the same size as the top of your heater outlet. You can buy replace flexible duct work to bridge the gap from you heater and the diffusers from LMCTRUCK or ClassicParts. ClassicParts give a 10% discount with the code stovebolt. There shipping is usually cheaper also. I just bought some. It was about $20. You can get something that will work for about $10 at Home Depot but it does not have the authentic look as the original black cloth duct work. LMCTRUCK and ClassicParts have the OEM stuff.

PIC if recirculating heater

Last edited by dgrinnan; 01/11/2017 1:56 AM.
Dave from Northern Kentucky
My 54 3100