steering wheel shakes

I have a 1997 ford expedition with 180000 miles and a 5.4 liter. The steering wheel shakes above about 65 mph and it feels like it's out of balance. I just had the upper and lower ball joints replaced on both sides, had it aligned, had bearing savers put in the rear and it still shakes (the bearings were a diff problem). I used dyna beads(balancing beads) and it didn't really help. I have 20 inch rims that have been on for about 5 years. I know it could be bent rims, messed up tires, out of balance, tie rods (which look fine). I'm wondering what to replace first. is there a way that a shop can tell me if the rims are out of whack? Thanks in advance