According to JD Sales Manual for 1978, cabs were standard only on 7700. And then it was only the tin box with windshield wiper and vent fan. If you wanted heat and_or air cond, those were options. 33, 44, 6600 were all ordered to spec as far as cabs went. There was ordering codes in cab section that included no cab, cab w_heater, cab w_ ac, and cab w_ both heat and ac. In some of 1970 advertising literature many of New Gen combines were pictured with out cabs. On further checking in handbook for introduction of New Gen combines, ordering info is same as 1978 model year.....33,44,66 even cab shell is optional......7700 cab shell with blower and wiper standard. Hope this helps answer question.