mk3/4 not 100% if shells are identicle or not, but they have diff front wings, bonnets, grills, headlights, rear lights, mirrors, bumpers etc

mk5/5b have diff bonnets, rear lights, boot lids, rear wings

mk6 has same rear end as 5b, diff doors, mirrors, bonnet, grill, headlights, bumpers, floorpan, dash, interior trim, front wings

off the top of my head lol