My guess is that my cranks don't use the French threads, they aren't THAT old. A 70's Motobecane probably DOES have the French threads. You could replace the crank, but by the time you're done it will have cost more than the bike is worth.
And yes, I kept my pants on. But the drool is always obvious when I talk to her. We're both married too, and I'd like to stay that way. She'll probably bring her husband along as he also rides.