I have a late 1980's Trek 420 in that size and a standard rear rack fits just fine. That frame has rear rack eyelets above the brake bridge. The description of the wheel size is off, the photo indicates that it has 700c tires on it as does mine. The frame on mine is True Temper tubing. With a rear rack, a fairly heavy seat/seatpost combo (Thudbuster LT seatpost), and wire bead 32mm tires, mine weighs in at 28 lbs. With a standard seat, alloy seatpost, the right rear rack, and 28mm folding bead tires on a small-framed 420 you should be able to come in at about 26 lbs or so, I'm guessing.