What must we keep in mind with Utility bed swaps?

I have had an aluminum flatbed and side saddle boxes for almost 20 years. I believe the aluminum alone might be worth more than what I originally paid for it. I measured the camper everywhere to make sure it would all fit. Make sure saddle boxes do not stick out too far and interfere with the camper tie downs, nor are too high. Watch the head ache rack height also under the cab over.