Ball joints will squeek while turning, but not usually over bumps, or something as simple as getting in/out.
I would suggest getting the T-Bird(98 year) LOWER control arms on RockAuto.com and start there, this will require an alignment afterwards.
If you wanna go all out, order the t-bird lowers, mark 8 upper control arms, and one strut rod to k member bushing kit, and one strut rod to lower control arm bushing kit. Than....get an alignment. You can also replace your tie rod ends if you want.