Fitting a front rack is always a challenge, and on those old Treks, it's worse than usual. I know, I have a 1982 720, and I've complained about this repeatedly. Can you get the legs of the Sherpa rack anywhere near the eyelets? Perhaps with a short spacer (not more than a few mm, that will stress the bolt and it will break). You should be able to bend the Sherpa rack legs in, make them narrower, to fit your eyelets; just don't bend them repeatedly. Bending metal once is not usually a big deal; repeated bending fatigues the metal. Also, look at the options of P-clips and U-bolts that might go around the fork and hold it on.