340 dart shifter help needed!

Ok so I just purchased a 1972 dart swinger with a 340 4 speed. The first drive after purchase had me under the car at a gas station trying to un bind the linkage as the car was stuck in we 2nd gear. the 2nd trip did exactly the same thing except the rod had come off the shifter mechanism. I limped the car to my buddies shop and we reattached the arm and unbound the shifter.we started looking and where the linkage attaches to the transmission, the paddles were loose and we're barely grabbing the notches on the tranny. I looked at tightening them down but the threads are warn out . What's the easiest , permanent fix To replace the threadson