Dually Bed
#1
#2
Your options are:
1. Live without a place to stash a spare tire, as well as with a 4" gap between bed and cab, which represents the difference between the 60" CA distance you have between back of cab and centerline of axle, versus the 56" CA distance that is typical of all long bed Ford pickups. That would look like this:
2. Fill the 4" gap with something useful and creative, like a headache rack roll bar attached directly to the frame, and at the same time come up with a way to haul a spare tire, like this:
3. Air chisel the heads off and drill out the rivets holding the forward and rearward leaf spring suspension stamped steel hangar brackets off of the F-350 chassis frame (unbolt front cast hangars and chisel /drill rear stampings if if F-450 chassis, unbolt front and rear cast hangars if F-550 chassis). Index and remove two piece balanced drive shaft assembly and have both segments reduced by an appropriate amount to compensate for a 4" reduction in wheelbase, keeping in mind that the carrier bearing may need repositioning unless an asymmetric prop shaft arrangement is made, and if so, keeping in mind the change in driveline angles in the loaded and unloaded state... Also, chisel and drill out rear shocks mount rivets on frame, and fabricate new shock mounts that will no longer have the benefit of the lower flange cut out for the upper shock rod cover to clearance.... Refabricate hard and soft brake fluid lines... re route parking brake cable and rear ABS tone ring cable... Cut exhaust system tubing, unbolt all hangars, before and after muffler, refabricate muffler hangars... Roll rear axle forward 4 inches... and, without going into tedious detail... rebuild the chassis from what you took apart... redrilling the frame for the spring hangars (don't forget overload cleats... and watch out for those fuel lines... etc.)
People have done this. But I don't have a photo to link, because you would not easily be able to tell the difference between a chassis modified this way versus an F-350 pickup up. I forgot to mention that you will have to cut off 4" to 5" from the rear of the frame rails so that the rear bumper will fit under the tailgate without sticking out weird. And you'll still need a place to stash a spare tire, due to the 40 gallon aft axle fuel tank. You can't replace the tank with a mid ship fuel tank for a pickup, because those tanks are made for 37" wide frame rails, and your chassis cab frame rails are only 34" wide.
There is, however, a couple of narrow frame mid ship fuel tanks from Ford that you can use, but one is less than half the size of your current tank, at only 19 gallons. And the other is not that much larger, at only 28 gallons. Compared to your current 40 gallon tank, that will be a significantly noticed reduction in range. Years ago, Transfer Flow used to offer larger capacity fuel tanks that mounted midship in narrow frame chassis cabs, including a 30 gallon, 34 gallon, and 50 gallon. However, those tanks were only available for diesel fuelled vehicles, and once diesel fuel vehicles began requiring DEF, sales plummeted on these aftermarket midship tanks on the Ford chassis.
My guess is that it is because Ford hasn't redesigned the DEF tank to fit under the CAB like both the Ram chassis cab and GM chassis cab, but instead leaves the DEF tank in the way of the upfitters, either midship between frame rails where a mid ship fuel tank would otherwise go, or outboard on the curbside frame rail (but still smack in the middle of the upfit zone). Therefore, in a Ford chassis cab requiring DEF, there remains no room to have both a midship tank, a DEF tank, and a service/utility body, an under bed toolbox, hydraulic oil tank, a welding gas bottle low load platform tray curbside, or anything useful that people buy a chassis cab for. I was stunned that an entire new 2017 chassis cab body and frame were redesigned without addressing this basic need that Ram already nailed two design cycles ago. Whoa I digress. Your 03 truck doesn't have DEF. But you'll still probably want to keep your aft axle tank unless you can find a midship tank that will fit the narrow frame.
4. Far easier than #3 above, you can detach the fiberglass dually fenders off of your donor bed, and reattach them 4" back, after banging up any sheet metal required to clear the tires at full jounce under full load, when the opposite end of the axle is in full rebound. You can get the clearance sped for this measurement from Ford, using the top of the frame rail as a reference datum line. There is quite a bit of wheel well space as it is, so the sheet metal work to adjust the inner bed panel wheel well might be minimal, especially if you stick with the stock tires. Sneaking the fiberglass dually fenders back, reattaching, and then filling the factory holes in the styleside bed skin that are forward of the fiberglass fenders, would keep the original chassis fully intact, and yet provide an aesthetic cover up to make up for the difference in cab axle distances.
5. Another "body work only" option to aesthetically cover that distance is to find the manufacturer of the forward bed fiberglass filler panel that pick up converters like "Roll - A - Long" used to convert F-450s and F-550s into ultra heavy duty pickups, before Ford napalmed that cottage business model in 2008 with the introduction of a factory built F-450 pickup. Here is a photo of what that fiberglass filler panel looks like. You have to really squint to see the extra vertical line about four inches aft of the cab. I've tried to use all gray trucks as visual examples, so that color will not too greatly influence your assessment of the aesthetic...
6. Compare the cost of selling the chassis cab with the vocational bed that is already on it, and use the money to buy a pickup. No matter WHICH method you choose, you will have to fabricate the manner in which the pickup bed is attached to the chassis cab frame rails. Nothing will bolt up. And you don't want to drill through the top flanges of the chassis cab frame, since the horizontal flanges are critical to retaining the strength of the frame, as they are the most stressed in compression and tension. Outrigger type of brackets will need to be made, that bolt through the vertical web of the frame, which is more neutral to stress than the flanges. It can be a lot of work, depending on how particular you are about the work lasting long term. Or it can be a great opportunity to create something uniquely your own.
#4
Your options are:
6. Compare the cost of selling the chassis cab with the vocational bed that is already on it, and use the money to buy a pickup. No matter WHICH method you choose, you will have to fabricate the manner in which the pickup bed is attached to the chassis cab frame rails. Nothing will bolt up. And you don't want to drill through the top flanges of the chassis cab frame, since the horizontal flanges are critical to retaining the strength of the frame, as they are the most stressed in compression and tension. Outrigger type of brackets will need to be made, that bolt through the vertical web of the frame, which is more neutral to stress than the flanges. It can be a lot of work, depending on how particular you are about the work lasting long term. Or it can be a great opportunity to create something uniquely your own.
6. Compare the cost of selling the chassis cab with the vocational bed that is already on it, and use the money to buy a pickup. No matter WHICH method you choose, you will have to fabricate the manner in which the pickup bed is attached to the chassis cab frame rails. Nothing will bolt up. And you don't want to drill through the top flanges of the chassis cab frame, since the horizontal flanges are critical to retaining the strength of the frame, as they are the most stressed in compression and tension. Outrigger type of brackets will need to be made, that bolt through the vertical web of the frame, which is more neutral to stress than the flanges. It can be a lot of work, depending on how particular you are about the work lasting long term. Or it can be a great opportunity to create something uniquely your own.
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