Just because it came 20th Campag doesn't mean if can't use anything else. It's just a matter of finding the correct 70mm Italian threaded bottom bracket for it. A lot of higher end Italian bikes in the 80's and 90s came with Shimano so there's hope.
As for the stem I would keep the quill and not get a quill adapter as their kind of hideous. Use your bars or if you like modern compact style bars check out the Soma highway One. They use a 26.0 clamp but have the compact bend like most bars do now to work with modern Ergo/STI shifters better.
Don't worry there's hope on updating your Gios! Check out this thread and it should make your head explode with ideas.
http://www.bikeforums.net/classic-vi...i-s-ergos.html