Our Ultimate K10 is mobile again now that fire is back in the proverbial hole. In its previous life, the truck relied on a custom in-bed aluminum fuel tank, a quick-fix way to get the K10 to the 2005 Ultimate Adventure. This 8-gallon cell served its purpose back then.
The goal this time is to make the Chevy a tow rig that can also penetrate the backwoods on its own. Reclaiming bed space is a priority, as is expanding the cruising range, so the temporary gas tank had to go.
This would normally be a nonstory: mount and plumb an OE tank and be down the road. However, this truck has rear springs 6 inches longer than stock, and the front hangers interfere with the OEM saddle-tank location. We like the longer springs’ improved ride quality and articulation, so they take priority. Mounting an OE tank in front of the spring’s hanger would require raising the floorboard—a day’s work to decrease the passenger’s legroom. (The wiring/plumbing is already routed down the passenger-side framerail.) Another tried-and-true solution for early Chevys is rear-mounting an S-10 tank between the framerails. That would also require a bit of doing on this rig.
Our project headquarters, GM Truck Center, measured several different OE tanks in its spares pile, then schemed an innovative plan: concealing a stock 16-gallon shortbed tank inside the Stepside fender. GM’s assembly line mounted the tank outboard of the frame, and suspending the tank higher theoretically increases safety by minimizing potential impacts. LMC Truck stocks the necessary OE and repro components, so parts are readily available to make this happen: gas tank (PN 32-5935), mounting straps (PN 32-5820), squeak strips (PN 32-5816), two-outlet sender for our EFI engine with return line (PN 32-4032), sender lock ring and gasket (PN 30-1290), filler hose (PN 32-3302), and vent hose (PN 32-3310).
Maximizing ground clearance is the main mounting challenge. GM Truck Center dimpled the tank and notched the fender flanges to mount the tank as high as possible. Factory frame straps and mounts were modified to suck the tank inboard. Obviously, bed sheetmetal alone can’t support the approximately 130-pound weight of the full tank. GM Truck Center used flat stock to triangulate the mounting straps underneath and to reinforce inside the bed.
The filler is another puzzle. New steel necks aren’t readily available, so GM Truck Center modified a spare of unknown origin to work. Our high-mounted tank leaves little space between its bungs and the fender. These bungs, the filler hose, the vent hose, and the filler neck were all trimmed or otherwise modified to work. (The vent hose controls backwashing during fueling, so it shouldn’t be bypassed or ignored.)
Plumbing was fairly straightforward. The sender wire was simply extended to the new tank. Pump duties (formerly in-tank) are now handled by an in-line Airtex unit. It’s compact for in-frame mounting but is high-flow to feed the Ram Jet 350. Aeroquip braided fuel hose and fittings are probably overkill for this application, but they will likely outlast the truck.
Now that the truck runs under its own power once again, next time we’ll move on to exterior upgrades.