40" is a lot, you may end up with water intrusion in the cabin, I think that is above the air vents at the back of the cab, when those get below water line it will flood ricky tick. Its higher than the door seals are intended to cope with. Aside from destroying your interior and trapping water everywhere there are some electronics in the cabin that might not like water.
The BCM is in the passenger kickpanel, so it should be moved, you will also need to relocate the interior fuse box, it is definitely not water tight and is low in the cabin. not sure if it is intended for submersion. You should consider removing the carpet, its just going to hold water and get ruined, you will want in non power seats, they will just short out on your first crossing. Probably a good idea to drill at least a hand full of drain holes both in the floor boards front and rear and under the rockers.
You will likely need to remove the rear seat completely since it is just going to be a sponge, drill holes in the floor of the jack box for drainage, then go in and rust proof all those holes. Your going to have to figure out how to waterproof the APPS sensor. Probably best to roll without door panels since they will just hold water.
When your in the water don't under any circumstances let off the throttle pedal. You will fill the exhaust with water, let off the accelerator and you get reversion... you will hydrolock it from the exhaust side.
