Hey man. Wondering if you had a ton of noise from the rear end before you swapped bushings. Got 125000 on my 13 mustang gt and I'm getting some noise, like popping noise from the rear suspension. Worse when cold outside, when it's cold every little crack in the road will cause some popping.
It sounds like you had the same issue I did! Check your swaybar endlinks and make sure the bushings are good and they are tight. Also check your lower control arms. I actually broke a bushing and bend my passenger side one. Those were my only issues.