Well what started as replacing what I thought was a bad electric fuel pump has turned into removing the old tank behind the seat and either cleaning it out and reusing it or removing it from the cab and relocating a tank between the frame rails behind the rear axle. I've got a couple of used gas tanks from 69-70 mustangs and cougars and thought about using those. One is really pretty clean inside, no loose stuff just some varnish stains in the bottom. Anyway I've been doing some measuring and what not and while I'd really like to run the fill tube out the back and hide it behind the license plate, I cant see how it will work but I know of at least one member who's done it. My delima is if the tank is even mounted on top of the bottom frame rail the filler neck is still going to be above the rear bumper area. I would have to cut a hole in the rear crossmember to run the filler tube through. I do know that one member has ran the tube to the driver side just in front of the rear most stake pocket and made a tunnel that mounts inside the bed with a removable lid on top to access the cap. This looks like a nice option but it looks to me like your still going to have to cut into the frame to make room for the filler tube. I've got less then 2 inches clearance between the bed floor and the top of the fram rail. I've added some pics.

 

Occasionally thought about moving tank, certainly would open space for options; i.e., I may look into an aftermarket A/C, or perhaps nice stereo sys??. After I flushed and treaded the cab tank many-many years ago have not found a need to swap.

Bookmarked a link to article in 'Classic Truck' mag. on the mustang tank swap if needed. Article mentions setting a fuel door in bed floor, do not believe I could go that route. As you mentioned, recall member installing filler neck on top of the styleside bed rail, if done right I thought it looks good, have seen filler door lids with same/similar contour as the top bed rail. Also bookmarked a thread where member installed the filler neck behind the drivers side rear taillight, which really looks nice, can post if decide to consider??

 

Ok 69supercj, here's my story....as you've seen in my other thread, I put a 92 Mustang EFI 5.0/AOD in my 66 shortbed. I wrestled with how I was going to provide fuel delivery for the fuel injection. Initially I explored the using the 2 electric pump system found on the late 80's F150's attached to my original in-cab tank, but I knew I wanted to eventually get the tank out of the cab. Mounting an in-tank fuel pump in the in-cab tank was out of the question due to the amount of noise it would make inside the truck!

So, I looked at all the options for mounting a tank under the rear of the bed. I definitely did NOT want the fuel filler in the bed floor because I still use the truck for work and moving all my stuff around just to fill it up seemed like a pain.
I found a guy on Slick60's who mounted a Mustang tank under the rear of his uni Slick 60's ? View topic - 62 UNI Take II

Like him, I wanted to have the filler tube behind the lisence plate and I didn't want to move that rear crossmember to squeeze the tank up between the frame rails. Driving around town I noticed many vehicles with the gas tanks visible below the back bumper and after taking many measurements I knew mine wouldn't hang too low to be unsafe. So, I moved ahead.

I bought a Mustang tank from Tanks, Inc because they had one already set up for the EFI in-tank fuel pump. It's only 16 gallons but that didn't bother me cause it would outlast my bladder on a road trip anyway.

So, I built a frame for it out of u-channel. I could have used square tubing in retrospect but at the time I thought the u-channel would work fine. I welded brackets to the u-channel to bolt to the crossmember behind the rear axle and used square tubing to house the bolts on the rear of the frame.

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The tank had a bolt on filler neck which I fitted with a piece of 1.5" exhaust pipe to get the right curvature to point toward the bumper. I have since replace that neck with the Tanks, Inc part #FN-PT Flanged Fuel Filler Neck - Hose Clamp Style to try to get a smoother fuel flow into the tank.

Here I'm fitting the tank under the truck. The amount it hangs down will be completely camoflaged by the exhaust pipes on each side.

After mounting the tank I figured out where to cut the hole in the bumper. I used this type of filler cap so I wouldn't have to remove it with most filler nozzles. Fill through filler neck




I found the fold-down license plate on ebay for around $20.


So, after painting the tank black with some bed-liner spray, it kinda disappears under the truck. It's a slow-fill (have to use lowest setting on gas nozzle) but I don't mind cause that get less air in the fuel than blasting it in at 100gpm! haha.




Hope that helps a little.

I just realized that last pic didn't have the exhaust so here's another....

 

Well I got the incab tank pulled out today and this thing is clean as a pin inside. Not sure what was causing my blockage. Guess I will flush it out with hot soapy water and let it dry. Also, which way do I need to bend my float level rod, more bend or less if its reading 1/4 tank when its actually empty.

 

Took the cab to the station today and found a small piece of solder inside about the size of a plump raisin and another smaller sliver of solder. I guess the larger piece was getting sucked up onto the bottom of the pickup tube. Got it flushed out and now its drying. I think I'm gonna put it back in the truck instead of moving a tank to the rear of the frame. And about the in-cab tank, anybody know what I could use to replace the "organic" looking insulating strips that go between the tank and the back of the cab? Mine look really compressed and not sure if they're doing any good or not. Thought about using foam rubber like you would use on the bed rails when installing a camper shell but I'm afraid that will squeak.