Andres, the carbs are Amal Mk1 930 concentrics. They are for a couple of 650 and 750 triumphs. So if I understand you correctly, you simply made up a new slide from aluminum. That would resolve the dissimilar metal issue for certain.
Moby Duck, I haven't seen or heard of a brake repair business in decades. There are still lots of brake shops around mind you but today, if a brake cylinder needs attention, it is simply replaced. Labor costs and liability issues killed the rebuilds years ago. I like your Norton tale.
Still hoping someone will address the issue of reaming versus boring. With my lathe I simply wouldn't be able to get the needed finish without sanding etc which throws out the hope of exact tolerances.