What year F550(chassis-cab) are you looking at? And what wheelbase?
For '19 at least, the F550 came with the aft-of-axle 40gal tank which all chassis cab's get. A diesel truck, only in XL or XLT trim(unsure why they didn't allow a Lariat trim get this "65C" option), could add the mid-ship 26.5gal tank, as seen on pg11 here;
Dual Diesel – combines 40 gallon aft-of-axle & 26.5 gallon mid ship tank (req. DRW; XL req. 96V XL Value Pkg. or 585 Radio on XL Fleet units)
Also note from pg3;
- Diesel Exhaust Fluid (DEF) Tank Location:
- ○ Aft-of-axle fuel tank is paired with the DEF tank located in the mid ship location, between the frame rails.
- ○ Mid ship fuel tank is paired with the DEF tank located outside of the frame rail
- ○ Dual tanks are paired with the DEF tank located outside of
the frame rail
Now, switching to pickup trucks, an F450 pickup (6.7L diesel only for F450) with a 176"WB (DRW only) could have a 48gal. See pg5;
So you could probably add the 40gal to it = 88gal total.
I cannot find any dual tank option for the '17-19 Ford SuperDuty pickups, only chassis cabs.
So, here's a rabbit hole....
#1 On your F550 project, if it was a '17-19 F550 chassis cab, and the 6.8L V10 (so no DEF tank in the way), it'd have the 40gal aft tank, but the rig would be a 179.8"WB SuperCrew (crew/quad cab) DRW (
https://fordbbas.com/vehicleModel/SuperDuty) vs a 176"WB...which means MAYBE you can fudge in the pickup's 48gal midship tank into the chassis cab = 88gal, but who knows if the tank would fit well.
#2 As mentioned above, an F450 pickup (crew cab only, DRW only) is only available with the 6.7L diesel, it is 176"WB with the standard 48gal midship tank (they must fit the DEF tank somewhere around it?), and then you can probably add the chassis-cab's 40gal aft tank in place of the spare tire. This is probably your best bet = 88gal total capacity.
#3 Or this is also interesting, see this thread;
https://expeditionportal.com/forum/...la-for-overlanding.222950/page-5#post-2898045 Titan's 55gal midship for '17-21 F250/350 SuperCrew(crew/quad cab) pickup, w/ 6.5' bed(I think Titan means 6.75' bed, as you can't get a 6.5' bed in '19 F-SD pickup), w/ 6.7L diesel. Now, per pg5 here (
https://media.ford.com/content/dam/fordmedia/North America/US/product/2019/super-duty/2019-Super-Duty-Pick-Up-Order-Guide.pdf), an F250/350 pickup w/ 6.7L diesel would either come with a 29gal (142" or 148"WB) or a 34gal (160" or 164"WB). But Titan mentions the 34gal being the stock size, so this means if you got a '17-19 159.8"WB(would be a CrewCab in SRW or DRW, 4x2 or 4x4) or 164.2"WB(would be a SuperCab in SRW or DRW, 4x2 or 4x4) pickup...but wait, dammit, remember that the F450 pickup only comes in CrewCab DRW w/ 176"WB (4x2 or 4x4), which means 48gal tank as standard from Ford. And Ford doesn't make an F550 pickup, only chassis cab, so no possibility of an F550 w/ ~160" or ~164"WB in order to get the Titan55gal + Ford40gal = 95gal setup.
So, for an F450/F550, probably no way to do a 55gal midship from Titan + factory Ford 40gal aft tank = 95gal total capacity. Someone could do probably this with the F250 or F350 6.7L CrewCab pickup w/ 6.75' bed though!! Would reduce the rest of your payload capacity with all of that fuel.
Or, for the F450 crew cab pickup DRW w/ 176"WB, see #2 for 88gal diesel capacity.
F550 (available in any of 3 cab designs) w/ 6.7L diesel will be factory dual only (26.5gal midship and 40gal aft) = 66.5gal.
Whew that was a lot of data.
