Buy this, or one like it. It doesn't use the BB threads. Instead, the bearing is pinched in the BB shell by the lockrings. You can see in the picture.
http://cgi.ebay.com/VINTAGE--MAVIC-B...02120819a23862
You're supposed to bevel the BB with a special mill. I have one. If you buy this BB, and live in the states, send me your frame and I'll do it for you.