2wd front disc diameter:283mm,4x4:278,both have 273mm rear discs. getting technical now though! final drives:2wd 3.64:1 4x4 3.62:1, and a nice easy one,non technical:different sierra rs badges on the boot,early ones have the same font as the 3doors with a half cut style font,later ones a bit more boring on badge side right,think thats enough to go on!