if you don't have a press here is another way to do it
#1 put the new ball joint's in your freezer for a day
#2 heat the lower A-arm's slightly with just a normal propane torch (IT'S NOT HOT ENOUGH TO HURT ANYTHING)
#3 find a peice of thick pipe or ? just something that will fit over the ball joint and rest on the metal lip of the A-arm
#4 sit the ball joint in the A-arm fresh out of the frezzer will the A-arm still hot and with the ball joint resting on a big socket or something hit the assemblie from the top thus driving the A-arm down onto the ball joint
hit it till it bottom's good and let it all warm and cool ,,,,,
someone told me that would work !