libila,
No problem. From what I understand in my research is that the early arms (85 to 86.5) only widen the track by 12mm +/- per side (my memory could be wrong about the exact number, but it's not too significant)
The later aluminum arms (87 +) widen the track 76mm +/- (again, from memory so don't take this as being 100% correct)
Someone like Zen can give you the exact numbers, but I have found them doing a search of the site. Suffice it to say that the later arms widen the tracking quite a bit more than the early ones.
I have a complete set of 944 Turbo brakes (4 pot Brembo) that I want to use, so replacing the arms with the aluminum (early) ones seems to me to be the path of least resistance.
Doug