[TxCajun]

After much thought, I decided to move the gas tank out of the cab to the rear of the truck, and make the necessary changes to the cab sheet metal prior to spraying some primer on the cab.

I looked at a lot of the gas tank related threads in this forum and ultimately decided on a Tanks, Inc TNK-51-CGX Fuel Tank, 18 Gallon, Steel, Chevy, (Mfr. #: 51-CGX) from Summit for about $170 and a TNK-TAN-GME Fuel Tank Sending Unit, 0-30 ohms, (Mfr. #: TAN-GME) for about $40. The tank comes with mounting straps, a short filler hose elbow, and a short length of vent hose. You also need to buy an npt-to-hose fitting for the fuel line, plus I bought some metal tubing and clamps for running the fuel line forward.

As part of creating and installing a receiver hitch, I had previously modified the "leaning Z" shaped brace that is riveted as part of the frame a few inches from the rear ends of the frame rails. I turned this in to a "C" channel by bending the top flange to 90 degrees, and cutting off the bottom flange, flipping it around, and re-welding it to make the bottom of the "C". This channel is then bolted to the back of the frame to box it in. The rear of the tank support straps are bolted to this piece.

To allow the gas tank to fit in from the below the frame (and make it possible to drop it out in the future without removing the bed), I trimmed the bottom flange of the side rails about 5/8” on each side and also trimmed the bottom flange of the angled cross member (where the panhard bar mounts) on the passenger side to clear the gas tank outlet fitting.

I fashioned the upper supports from 1” x .062 wall square tubing; I made these supports removable rather than welded in place so that I can also remove the tank from the top if the bed is off.

I fabricated brackets from steel angle for mounting the front of the lower straps that support the tank to the angled cross member.

The pads that were between the existing cab tank and straps were in pretty good shape, so I trimmed these and re-used them for isolating the new tank in its supports.

With this support arrangement, the tank hangs down below the bottom of the frame rails about 3.5 inches.

I cut some reliefs on the upper flange of the driver side rear frame rail to allow clearance for the tank fill line and the vent line, and then fabricated a brace to add some strength back in to this area while also protecting the lines. My intent is to eventually create a fuel filler feature inside the rear corner of the bed, so I'll need to extend the fuel filler line and vent line to that area.

The photos below show the mounts tacked in place and the tank mounted for a test fit. I'll drop the tank out, finish welding everything, brush on some frame paint, and then bolt it back up.

When I get ready to install the bed at some point in the future, I'll need to trim the rear bed brace to fit around the tank and upper supports. The bed floor on the truck is steel tread plate rather than wood.
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