I need to do this to a frame. I usually put the bb shell on a post and bend it that way, but in this case I haven't figured out how to get the bb out. Apparently takes a special tool. I started a thread on it in here while back, it's a Dutch 3 speed and it's currently spaced at 140mm
I'm usually a little obsessive about bending frames. A framebuilder I respect always recommends the axle method, but I figure that on older bikes the drive side chainstay is almost always more compliant than the non-driveside chainstay due to the extra dimple for crank clearance. So it will never work