Try just beating the hole shut from the sides. The weight of the truck and spring pressure will hold the a-arm down on the pall joint, so the ball joint fitting supper tight is not really important. You want it tight enough to hold, but supper brand new tight is not necessary. You could also tack weld the ball joint to the arm till you can find a replacement. As long as the ball joint is good, the nut is tight, and ball sock is good and tight, it won't come apart while driving. For really rough off road use, look at some of the off road sites for heavy duty parts.
Joe
