Just a switch? Cut yourself a rubber ribbon from an old inner tube and wrap it around the bar. If you accidently whack it, it ill usually let the switch move instead of damaging it.
Index shifters need modern linier core housing, brakes and old friction shifters usually work fine with the common cheap spiral core. I tend to clip them with heavy duty wire dykes and open the holes with an ice pick, but an angle grinder definitely works better. As for housing ferrules...
If you ever come up this way again let me know so I can unload a pile of old frames wheels various parts perhaps some dirt cheap or free whole bikes on you. :crazy: :rofl:
Did the same on my old 26" Good Vibrations10 spd. conversion. Had no doubt it would work, after all the front wheel always goes past the brake that way.