Porsche doesn't offer changes that often. I recall the change from 1973 to 1974 and thought they had lost their minds! Little accordians on the sides of that impersonal massive bar of a bumper? What were they thinking??

Here are the body changes of the US Market) 911 over the years:

1965 Introduced
1969 Wheelbase extended
1974 Newer bumper protection/black trim introduced
1978 Carrera rear flares for everyone!
1990 Cleaned up bumpers fore and aft
1994 The beginning of the end,--the 'new 911' a la 993
1999 Add water
2002 Change some lights, add glass to the cab window (minor)
2005 the 997 comes to light

Dan