Mine had rust holes in the floorboards. One from a leaky heater, other from leaky cowl. You might get under the truck and have a look see. This is where the floor board makes the bend up from flat. Its an easy fix as its going to have carpet or mat on top you can just slop on a surface fix. The other problem tho is if its on the corner, then its a bit more work to fix. Also the flooring has a bit of a bend to it going towards the outside of the truck so water will collect at the joint.
The cab mounts in the rear of the truck also can rot. Reach down the cab corners and feel towards the inside. Bet its paper thin there if not already holed out. If not, you are fine. But be careful as it could be jagged down there.
