My GT is an american spec, but when I changed out the rear end(the car's, not mine

), the scrap yard one I got had the brackets on it. I got the front and rear swaybars from OGTS and it is a night and day difference. I run stock tires(165-13's) and the car rides like it is on rails now.
So to answer your question, yes, it does handle differently(better) with the sway bars attached.
I also updated my front and rear suspension with poly bushings which also tightened everything up.
HTH
Jeff