Mark is correct; MAFAC variation of reach is accomplished by the étrier. Good luck finding anything with "grand" étrier; however, I believe that the Racer, Competition, '2000' and 'S' all used the same arch, so if you can find any of them with the longer reach, you'd be OK. All of them except the Competition go to 68 mm with the grand étrier. You're right about the part numbers, though I'm not sure those are stamped on the arches.
while I like MAFAC brakes, I think that the Weinmann's approach (having shorter or longer arms to effect reach) is more rational, though it messes with the mechanical advantage a bit (OK if it's the rear, as is most commonly the case).


For the whole poster:
https://www.flickr.com/photos/131757...7628023244738/