Paul,
          Did read on this forum about someone who used
the cooling tube from the muffler to heat the cab. I am
currently trying to see if I can get rid of my cab water
heater which is really quite heavy when the water is added.
So I can either take heated air from the muffler area which
I do not like due to the possibility of CO gas, or somehow
get hot air from the rad exit.  Does anyone have
experience / advice on this matter ??
                            Neil.

Neil,

I recently converted my water cabin heater to a heat muff.  I made sure that
the "muff" was over a section of pipe that had not been welded.  I also
installed a CO detector in the cabin.  While a quite expensive little
device, I figured what is my life worth?  This change eliminated about 10#
of weight (water included).

With that said, I don't think the air coming off the water radiator is warm
enough to be much good at heating the cabin.

Mark