It's easy to do on the outside. It's the inside that makes it hard. I had to put a new roof on my 63 big window with a roof from a 63 small. I took the inside from the old roof apart at the upper seam and welded it into the roof of the small window replacement roof. I've never tried just a conversion, but I would bet money you'll have to find a donor to get the inside sheetmetal to make it look factory. Once you have the two cabs next to each other, the difference is obvious,
Scott
