Stabilizer Bar Bushing
 

Hello,
i have to change rear bar bushing , but on rockauto they have only 2 sizes. For 19mm and for 22mm sway bars.
As i know for 2008 gt stock sway bar is 20 mm. Am i wrong ?

Measure yours and then order a Ford performance or energy suspension bushing.

If I remember right, the stock GT bar was 22mm. When I upgraded my rear swaybar on my GT to Steeda (22mm), I reused my stock hangars because it was the same size.

LMR backs this up too. According to their size guide, the stock GT swaybar is 22mm.

https://lmr.com/products/Mustang-Sway-Bar-Size-Guide

As far as the 19mm bushings go...maybe for the V6? LMR lists stock swaybar sizes for the pony package to be 20mm and the V6 vert to be 18mm.

Best way to be sure is follow Jazzman's advice and measure it.