If you do decide to go with a long reach brakes, hopefully you can go with the brake prior to the one FBinNY showed in his link. I have used this brake (still have it if your still interested) and disagree with SB; it would not lock up my rear wheel when the bike was being pushed; as FBinNY said
The problem is that long reach brakes don't work all that well because the long arms are much more prone to flex than their shorter counterparts.
The Tektro 984 long reach
http://sheldonbrown.com/harris/brake...ers.html#70-88 works significantly better. you need about 3.5" (88.9mm) and the Tektro have an 88mm reach.