Some 1991 3/4 ton 4x4 suburbans have rear cargo doors vice tail gate.
With rear seats down it will hold 4x8 plywood. If you choose to
sleep in it safe from weather, and crawlers and biters, it is convenient
to enter and exit the rear cargo doors.
There is no inside handle on the rear cargo door. Remove the panel
on passenger side cargo door, look through the access hole and
see things move as you press thumb button, and lock and unlock
the door. You may reach through access hole to lock, unlock and
open the door from inside.