There are bolt on ball joints for the lower control arm, but mustangs originally came with them riveted in place, and it is not fun to remove those rivets.
The whole arm can't cost that much, and you would have the extra comfort of knowing you had new ones.
Oh and screw advance auto parts. They totally hosed me on a steering gearbox.
Store manager:
"You should have come by and check to see if the part was in."
Me:
"I did check in with your people, everyday for the last two weeks I either came by or called."
Store manager:
"No you didn't, or you would have your part."
Me (surprised by the managers raising voice and sudden hostility):
"Huh?"
"Did you even order my parts?"
Store Manager:
"You never came in to pick them up. It's your fault you didn't get your part."
Me (figuring it out):
"Ok well if you didn't want to replace the defective part you sold me before you should have just said so and I would have gone elsewhere to get what I need, like I'm going to do now."
Store Manager:
"Good!"
Me:
"Thanks."
Man was I pissed. I haven't been back since and that was three years ago now.