The original forced air heater has a few draw backs. One of which I experienced first hand. The whole vehicle was a true work of engineering. However, like all other things, there were a few oversights. In the past there have been studies about carbon monoxide entering the cab because of failed exhaust packing. I can neither confirm or deny that, although my original 1961 packings arent leaking. What I have personally noticed, is that even the slightest oil leak, residue even, will cause quite a stank, and sometimes visible smoke, inside the cab. I know there is no reason to have any type of oil leak, but realistically, sometimes you just can’t tend to a leak immediately. Frankly, burning oil gives me a migraine. The third thing that bothers me, are the lower engine covers that are required to use the engine as a heat source. Generally, I like to be able to see my cylinders and I am also thinking about running some headers and not the factory log manifolds. Also, since I live in a high traffic area, the extra cooling from leaving the covers off would drastically improve reliability. I’ve been keeping an eye out for an original GM gasoline fired heater. There was one on ebay for a while for $400, the working condition was unknown. Then, there was one for $100 that was sniped within hours of being listed. The other day, I found one that slipped through the cracks. $142 shipped to my door. Condition is unknown, but it looks really good. I don’t think its coming with the controls, but I’m least worried about that.