Originally Posted by
NormanF
There's a bottom bracket drop of 4". Isn't much if the bike was originally meant for 27". You do need new brakes but a conversion usually poses no real difficulty. The only limiting factor is how big a tire you can mount on a 700C wheelset.
I really doubt the BB drop is actually 4 inches! that's 100 mm of drop, which is not at all common. Have you measured it? Pedal clearance is not the only thing going on here - greater BB drop moves the down tube closer to the front wheel, reducing the clearance between it and the wheel. Addition of a fender can reduce clearance considerably. Ameliorating the small clearance could involve moving the head tube forward or laying back the head tube. The first measure results in a long, sometimes too long, top tube, and and the second can affect steering behavior (flop).
In road bikes DeRosa and Richard Sachs are about as low as anything, and they use an 8cm drop. That's already lower than just about any other modern road bikes.
Plus, if the brake slots are long enough to adjust the brake shoe position 4 mm downward, why would he need new calipers? Do you know for a fact the existing brakes won't work? I would not want to give the OP advice that will cost $$, without full justification.