I want a ladder rack like this one.
TLR3 Pickup Truck Ladder Rack - 3 Ladder Capacity
But I don't want to drill holes in the bed of the truck. I have 4 square holes with slots on the inside of the bed. Square tube ought to fit the square holes already there with a reinforced threaded bolt hole. They should go at $50 per pair with a good coat of powder paint.