as the title suggests, what exactly is the difference between the gt30/40 and the 35/40? both being the 1.06 ar rear, wheel sizes i know are different, but just the rear wheel or both? and the 35/40 has an extension on the back of exhaust housing, is this the case with all of them, can i tell whick is the 35/40 without the serial numbers, as the front cover is polished? any help would be ace, please only give info if you are quite sure.