This is a can of worms, you really don't want to open. I've got an early 80's Univega Gran Tourismo. It came with 27" wheels and DiaCompe canti's. It crossed the US E-W fully loaded, successfully and without incident. Couple of years later, I bought a 'racing' bike and it was relegated to the ceiling of the workshop. Years passed and I needed a commuter, so down it came. The 27" wheels were long gone, so I 'upgraded' to a set of 700c's. From then on I fought continually with the canti's. City bus noisy, poor performance. I tried a new set of canti's and they were even worse. Put the original DiaCompe's back on and they sort of worked. Toed to the extreme, they were at least quiet but they were not very confidence inspiring when it came to stopping. After a long correspondence with Paul of Paul's Components, we both came to the conclusion that with the particular frame geometry anything 'modern' was not going to work. Sadly back to the ceiling it went. I then retired and spent more time in the workshop, it cried on me daily. Finally I decided to restore it. Powder coated the frame, polished all the clamp on bits and bobs and built a set of 27" wheels. I had a set of Shimano 200GS (BR-M201) canti's in the take off box. (The Dia Compe's looked like sh*t.) On they went. Result was braking Nirvana. Quiet and responsive. I can even lock the wheels! My old buddy's back on the road and working and looking better than it has for a long long time.

Moral of this story. There are cases where you really can't teach an old dog new tricks. 27" wheels are 'not cool' and tire selection is severely limited but sometimes they are the best product for the job.