you probably need a new arm and balljoint since they screw into the arm, they do not press in. you can buy the appropriate socket from mancini racing or the usual verdors like snap-on or mac (but they can be a bit pricey from them.) i'm netting the threads were wiped out during installation. you COULD weld the joints into the arms if you don't go too crazy and get them really hot. some good tackwelds should do the trick if you allow time for them to cool between welds. be sure to take the boot off when doing this. it'a a one shot deal, but what do you have to lose? except control over the vehicle when things come loose again.
but then you already know that. 
i drove my '63 dart vert for a few hundred miles with an exhaust clamp around the bottom of the joint to keep it in place (hey, i was on the side of the road!), then a couple thousand more welded in until i swapped BBP discs on the car.
-james