Tbh polybushing makes a massive difference, i havent yet done the rear beam mounts but i will be as i want the whole car to be polybushed. I have a 24mm Whiteline ARB on the front and whiteline droplinks and its a very well worth upgrade and i have heard that a rear ARB Is a massive must! one of the best suspension mods you can do. I also have a ATS 2-Way LSD which is my fav mod on my GT