Extra-long recessed nuts are made by Problem Solvers and may be found in the QBP catalog (that any LBS can order from):
http://aebike.com/page.cfm?PageID=30...and=312&type=T

I'm currently running a recessed rear brake in the front using one of these nuts.

For a vast majority of brakes there's no difference between front and rear. However, current high-end Campy road brakes feature a dual-pivot front brake, single-pivot rear brake. They call this a 'differential' system.