the bushing is squeaking and worn out is because it's constantly subjected to twisting & flexing under the suspension cycle.
If you replace it with something super hard/stiff, then those torsional/flex/twisting forces are going to be transferred to the mounts, which will rip them apart.
So, you want to use a track bar that will account for the torsion/twist/flexing by using a flex joint, yet provides the stability and clearances necessary. After going through the same issues, and major clearance issues with the same JKS track bar, I made my own custom bend track bar utilizing the original stock bar and a heim joint.
But for those not wanting to custom fab something, there are some better options. The new bend Currie rear track bar is supposed to address the clearance issues, and it uses a Currie Johnny Joint to account for the misalignment. It also requires using their relocation bracket.
Give these guys a call for more info:
Regardless of the route you go, you will need to check the clearances at full bump. Here's how I did mine: Unlimited04's LJ Build - Page 24 - JeepForum.com