SD50 and SD60F's are special cowled wide-cabs units which with the way they are constructed they are lighter than other models. Nobody has made any cabs for these models that I know of. SD50F is the only wide-cab variation of the SD50, where the SD60 has the SD60M, SD60I, and SD60F. SD60E is a rebuild project of SD60M's, so there's really nothing special there other than the way the windshield looks.