It's the square taper on the arm that's wrecked, hence needing a new crank. I thought I could get away with just tightening it, and that's what chewed up the bolt. I'll look for a replacement on the buy and sell.
Thanks for the wisdom!
Any Campy square-taper crank will fit your BB. It may be easier to find a whole crankset, though. (I've seen a couple at the Portland used-parts places.) Just remember to torque the bolts to 25 to 35 foot-pounds, otherwise you'll hog out the crankarm again.
FWIW: I have a '70's Campy crankset (no BB) I should sell, but I'm too lazy. It's 175mm arms, though.