I was partners in owning a truck equipment shop. We built so many flatbeds I couldn't begin to count. Some were awesome, most plain Jane. A few that had ideas the customer wanted, that I made them sign a waiver. The exhaust through a headache would be in the waiver dept. it could look cool, but protecting stacks would be better than having corrosive action in a structure IMO.
One supplier you all should look at before building one is
http://flemingmetal.com Their website is not real good. You need to call them and see if they still mail out their paper catalog. Thier flatbed components for rails, crossmembers, stakes,etc. are top notch.
One person can easily handle all the parts to build a 20' flatbed alone, all welding can be done in one position until it's time mount the bed. Strong and lightweight.
When it comes to underbody boxes, my theory is mount the largest ones that you can fit, and filling in a body line with some sheet steel and a few braces always takes just another flatbed from plain to very nice quickly.
On back end my 2 preferences are either a classic semi truck style 3" channel iron ICC Dock bumper hanging flush from the back, mounted to the frame end for the simple look. Best is a sheet of 1/8" flush to back, come straight down a few inches then tapered in as a trapezoid, like in treegump's pic. Frame it in 2" square tubeing, only with the tubeing in front of the plate, not to the rear. People will try using it as a sep and slipping off. If you want it sticking out like his pic, it needs to be bigger than that, which gets in the way.
Recess the license by cutting a rectangle 2" wider than the plate, frame it 2" deep using the 1/8" plate. This lets you put the 2 plate lights (required by most states) on either side and all is fully protected. Even fancier looking is angling the plates all @ 45* like a picture frame, and no mud or water collects to rust.
Same goes for mounting 7pin connectors- don't let things get smashed by design, function always can look better if you take the time to trim it out.
D rings are always useful, but if time is taken to recess them in same manner it looks super custom, and you can work the rear of the truck without things in the way. Make sure you tie in to the frame with your d rings always. Usually they can be inline of supports to the hitch. If hanging below like in the pic, mount them directly to the hitch cross bar.
If you aren't always swapping draw bars, flush mount the hitch, your shins and everyone you know will thank you for the extra effort.
Buying a bolt on hitch and working around it is a good liability idea. Lawyers can take your lunch money if something goes wrong, usually someone rear ends you, and your hitch sticking out causes extra damage. If you bought it the lawer can't chase you. I've been pulled into court a few times and 2 things are questioned. Hitch and whatever cargo/material that they did not tie down good enough and went through the windshield injuring the occupants.
Tie downs- make it so easy to use, that you ALWAYS use them. If you have workers in your trucks- unsecured loads will end your business or worse. Take this one serious folks. I've watched a company doing over $10,000,000 a year in profit go down the tubes because there was not an easy way to tie down a 4' ladder and a 5 gallon bucket.
Headache rack- the biggest mistake I made is a common one. We always used 3/4-9 expanded metal IN FRONT of the rack welded at each junction. Looked clean, and strong. Until years later and the paint wears down. Then it's a rust dripping, unpaintable mess. Make it on a frame of flatbar that can unbolt from the rack. In 4-5 years you'll thank yourself for the extra effort. So will you window guy if one ever gets broken. I did one bed remove/ install every 3 months for glass companies. Think your upset at a $200 window, wait until you pay for that extra charge.
Always make your rack follow the body line of your pickup unless you want it to scream "generic commercial fleet bed".
If anyone has a paticular problem on design, ask. I might have done it before.
@schiker take some pics of your interior and what you carry. Pm if your worried about local thiefs seeing forum and recognizing your truck. There's always a solution. The truck owner finding the solution almost never happens, or they wouldn't need a solution. If nothing else my ideas might make you laugh.
