I think the extra length is split between the inside and outside; but I think the matching arms make up the difference...pretty sure the first change in wiper posts happened in 9-73, and again in 9-77, although I'm not certain the change between 9-73 and 9-77, I believe the 9-77-end of model may have had a fatter stud on their pivot; that year range requires different arms than the 9-73 - 977 arms, although the plastic pivot covers seem to fit 9-73 - end of model pivots...clear as mud?