I'm no bike expert, but I've spent my life in engineering, so I may be able to help you out.
What sort of brakes?
Is it a single centre pin or two that hang off your stays? etc. etc. Private message me through here and I'll do my best to help you, although other people will also offer some very valuable (and probably better !!)/experience as well on this site.
I have drilled a steel fork to take a mudguard. Took bloody ages and the result (due to breakage of several drill bits in the process) wasn't all that central. This was OK for a mudguard - but would be worrying if the hole was for brakes, which really do need to be spot on central for them to work well and not rub etc, so I wouldn't advise you do it yourself. I was told (by LBS) that depending on which fork you have, drilling it could actually compromise it's strength. My fork was basically scaffold tubing (and was already bent anyway) so probably no harm was done, but a lighter weight fork may have suffered. If you have the bosses for Cantis or V-brakes why not use them? You can get Dia Compe V-brake levers which work with drop handlebars if you want to use V-brakes, but modern cantilever brakes (that you can use with ordinary aero brake levers or STis/Campag Ergos) are very good - especially the 'frog legged' ones where you get greater leverage.
Thanks Blonde, I know what you're saying but unfortunately I don't have bosses.
I've got a 1979 peugeot road bike that takes NUT fitting brakes, I require to place new modern ALLEN KEY fitting brakes in there. I just want to know what size to drill it out to, can anybody measure there bike for me??
Yup, did one about 1/2 hour ago 8mmm drill and a drop of oil, took about 30 seconds. The modern brake fits perfectly into the elongated allen nut. You will of course need to put the front brake on the back and use the back ( with the shorter threaded stud length ) on the front. I did another a couple of months ago and have used the bike pretty regularly with no probs. Theres a big thread on it at the CTC forum somewhere, and good old Sheldon B has something to say too. Hope this helps.
The case hardened long nut ( for want of a beter description) with allen key head is about 50p from most bike shops - its about 27mm long and is especially made for that conversion