I had mine apart a month or two ago. I had the same experience and if I remember right the frame end of the arm is not centered on the knuckle end. It was my impression that this bushing not only adjusts camber through the eccentric center piece but also keeps the upper arm perpendicular to the hub through the reverse installation of the inner bushing from side to side. Moral of the story, yes the arms are the same, the bushings are the same but the bushing goes in differently from side to side.
If you decide to change these out, they are a bit pricey (I paid ~$45 each) and can be tough to get out. I dismantled each using a chevy wrench (big hammer) and some sockets until I was down to the inner sleeve. Then I put a hacksaw blade through the shell and put the hacksaw frame on afterwards. After a little cutting (being careful not to cut into the arm) I was able to collapse the shell enough to get it out. The new one slid in with just a little convincing...Good luck...my wheel hop is significantly less now that I replaced the knuckle and upper arm to frame bushings...
Anthony