I had a unique situation to deal with, this truck I bought to haul my truck camper in, had a 5th wheel installed. These photos will show how I dealt with this.
I took the the wheel out of course, but I left the rails in. The rails are bolted to the frame of the truck and would be additional strength. Beside I had no interest in taking it out. I got on RV.Net and saw how others had done it. I got two sheets of 2 inch pink polystyrene foam, cut 1 in three pieces, then glued them together leaving a space for the rails. Its worked perfectly.
I got the benefit of raising the camper up another 4 inches above the top of the truck cab. And as I’m working on the bed mounted battery system, it provided a convenient way to run the electrics under the camper to the other side of the truck where the way too small batter box and hookups are. The battery location is the only place in the truck they will fit with the camper basement configuration. Looking for plastic container for them, Bass Pro doesn’t have anything big enough for those two Trojan T-105’s.
Tip on the wire… 20ft, 4 gauge booster cables at Walmart, $29, with the ends cut off. That's 40 feet of 4 gauge for $30. Save 25% over buying bulk wire at the Depot.
Those are my torklift tie down extensions in the bed, removed them while not in use. Just way to easy.