The '63 Bambi I once owned had the same gravity furnace that is shown in the detailed photos of this Bambi listed in the classifieds currently. This is the URL to the photos, and they show many of the details of the interior, as well as the heater. Mine, along with this one, did not have a fan, or even a thermostat. You lit it, and it was on. Period. I sure as heck would never put a NT 35 in a Bambi, way, way too large, heat output and physical size. The Suburban 16,000 Btuh output would be fine, even overkill.