I have seen pictures of 100s with 100-6/3000 front fenders. They are the same size and overall shape. I believe you would want a pre-roll up window fender. As I understand it, there were changes to the a-pillar and, therefore, the rear fender mounting flange to the a-pillar, in those later cars. One would also need to create a small recess in the six cylinder fender to accommodate the forward "foot" for the windshield.
I have also measured my 100 and fender length is also ~63"
For all who wonder where the extra two inches went when the wheelbase was lengthened, it's in the interior. The doors are two inches longer in the 100-6/3000 than in the 100.