A leak inside the case could be absorbed by the fiberglass and lead to rust. (Don't know for sure, but just seems likely) The insulation was missing from my heater when I rebuilt it. I didn't use any in the heater. In fact, I didn't know it was supposed to have the insulation until I read about it on Stovebolt.

I don't know of a source for the rubber gasket. May need to cut one from bulk rubber. Perhaps someone who has the heater out of their truck can trace a pattern for you if yours is missing.

Keep plugging away. I enjoy your build info and refer to it for help with my '54.

- Lonnie
My '54 3104
Photos that I have shared on Stovebolt via PhotoBucket are no longer available. Please contact me if you want a photo from an old post.
lonniecook [at] aol [dot] com. I sold my '54 3104 12/12/2017, but I still visit Stovebolt.

OLD STUFF ... houses, furniture, cars, wine ... I love it all