I have a fork for a 27 inch wheel on my fixed gear and recently switch out the wheels for 700c. I have this nice pair of 105 brakes that I wanted to put on but put on these old long reachers instead because of tire fit. Is it possible to replace the fork with one that is more compatible with the 700c tire thus allowing me to use my 105 brakes as well as have enough clearance for my fenders?
Unless you specifically have long-reach 105 brakes (they were available) I don't think you can find a fork that will allow full fenders and short reach brakes. There are fenders that have cut-outs in the fork crown area to clear short reach brakes and tight clearances but they aren't real effective.
BTW, Shimano and Tektro both make current model double pivot long-reach brakes and these may work with your current fork and the 700c wheels. I converted an '83 vintage Trek from 27" to 700c and the 105 dp long-reach brakes on it adjusted far enough to line up properly.
All you have to do is to find a fork that has the right offset and dropout to crown dimension. Uh - that might not be an easy thing to do.