methinks it can be done!
thinking back to real post office days they used sherpa vans with roller shutter doors fitted sometimes,
all it was, was the runners for the roller shutters were fabricated into the rear door opening just inside the back.
If I can remember, the roller mechanism had the roller storage box at the top that was just proud of the rear roof line.
But It would need a sealed bulkhead between you and the doors coz of fumes being sucked in.
it would make you sleeeepy before you just died!