balboa shouldn't be too tough to find
the big problem wiht the columbias is they are fabricated really weird, they use an odd headset with like lawnmower bearings... might even have bushings in there? i cant remember it was some junk. and the frames are just super flimsy.
you'll want a tube frame rather than stamped because its way easier to get a good weld to hold on it, if you weld on the sheetmetal it has way more heat distorion and its not structurally sound... you can braze on the stamped frame bikes