Swapping brakes and levers
I have a randonneur bike from the 1980ies which still has many of the original parts. As far as i can tell it still has the original calipers and brake levers (shimano 600 ex or something similar, with cel 60 levers that go perpendicular in front of the handlebar; the caliper just says dia compe, it might be a dia compe gran compe 400). The brake shoes have been changed of course, but still the brakes are not very good. Trying to adjust the bowden cables didn't change much.
I'd like to take the bike for a tour across the alps, and am trying to figure out how to improve the brakes for it to feel safe. Does it make sense to change them completely, or should they still do their job well if set up correctly? If they should be changed, what do I need to consider when changing them? Since they are screwed onto the handlebar, would any modern break lever fit? What kind of brake should I get for a good improvement in brake strength if I don't want to go for disc brakes?
@adamrice@c.im‘s advice is excellent, came here to recommend a cheap alternative: get yourself used shimano breaks from the 90s off of ebay.
These for example will brake better than the brakes you have installed on your bike and cost EUR 37. Search for Shimano 600.