It will fit, I think the shock is slightly longer pre 07. So might raise the seat a bit, but a friend rode A level enduro with an 05 ohlins shock in a 2010 without any drama.
my 2000 ohlins is at least 1" longer than the sachs on my 07 - are there any issues with switching???? i would think it would change geometry pretty drastically...
There are different lengths over the years. '03 saw a drop in the upper mount position and a shorter shock body length. '03 up should be good, just check the shaft travel.