Make sure there is no paint above the spring plate on the canti boss. Remove the spring cover and spring and slip the brake arm over the brake stud. it should slide all the way down to the shoulder on the stud with about .010 of the stud protruding above the brass bushing in the brake arm. Don't use a file to clean up the stud use 400 grit w/d sandpaper.

Those old XT2's were great brakes I still have them on 3 of my bikes