look along the chassis rails and at the back base of the cab
the luton itself look at the shutter if it has one and pull it right down if the shutter
doesnt follow along the bottom flush with then the chances are the body could be twisted
if its barn doors they should be inline along the top and bottom when there closed if its sitting
on a level road if its on a incline move it on to a level road and check the wireing that follows along the chassis to the rear lights make sure it aint butcherd and check teh plogs that run in to the rear lighst aswell they often pull apart and make ya think the wireing is knackerd when its only the plugs needing pushed together
also if its a ali or GRP box check the actual floor of the luton the bit above the drivers cab if it is loose or drops down when ya put weight on it will mean its sprung so the support spars that are underneath it will drop down and rub on the cab roof and make it rust out, check the floor roof and walls inside for any signs of water damage as it will rot the floor aswell
depending on what weight and how its been treated luton bodys are usually pretty solid
just look for any damage on the chassis for any signs of the box being removed in the past and maybe having a bigger or shorter lengh box fitted to it
