I'm not sure Butane is even commonly available any more - sure isn't anywhere in my area...
Conversion to Propane is no big deal - just a few jetting changes usually...
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John Day....|'88 Winnebago Super Chief 27ft. Class A
Eastern .....|'88 KIT model 240 24 ft. 5er
Oregon ......|'02 Dodge/Cummins 2500 Quad Cab