here's a real simple solution (to me anyway), providing that you are willing / capable of making this an actual functional gas tank.
go on e-bay and look for one of these tanks (it's off of a jesse james west coast chopper bicycle).
I picked mine up for $7.00 plus $8.00 shipping and it looked like this when i got it.
they are made of pretty thick steel and they are very hefty.
now, you will have to be able to weld, braze or silver solder all of the holes and gaps closed to seal the tank up. after stripping the whole tank to bare metal, I used silver solder and a propane torch (you will need to use acid flux for the solder to stick.)
then you will have to cut a hole in the top for a gas cap. I used a push in oil fill cap for a car valve cover. it has a rubber plug on the back side and it seals well in the hole that i made. I drilled a small hole in the top of the cap for a vent, and covered it with a pewter skull that has open eyes so the vent actually works.
you will have to pressure test the tank with compressed air and water to check for leaks. once you have it all sealed up, you can procede with making it a functional tank.
I then ground down all of the ugly welds that were on the front of the tank and filled the area with bondo.
I drilled 2 holes in the lowest points on the rear of the tank (one hole per side) and i soldered in 2 peices of copper tubing to make fuel line outlets. you have to put one tube in each side of the tank because the tunnel inside wil not allow gas to go from one side of the tank to the other.
Once the bondo was all smoothed out (i sightly re-shaped the front of the tank), it's ready for primer and paint.
here it is next to a 66 triumph bonneville tank for size comparison.
Once you get a couple of good coats of primer on it, you can paint it.
I used 5 coats metallic black laquer, 5 coats of clear, wetsanded and buffed out.
to hook up the fuel lines, you will need to get a T fitting so you can run the 2 lines into the single carb inlet. Use a single in-line fuel shut off valve after the T fitting, and 2 inline fuel filters before the T fitting.
I repainted this tank meatllic silver with pearl clear this summer and here's how it looks now.
here's another one i did for an actual jesse james chopper pedal ike. There was no need to seal this tank all up, but i did grind down the front welds, smooth it all out and add a fake gas cap to it.
This one has 5 coats of metallic orange laquer over a silver base color, and 5 coats of clear laquer.
you can do anything you want if you use your imagination. A gas tank doesn't necessarily have to start life as an actual gas tank.
you can pretty much make anything into a gas tank as long as the material is impervious to gasoline.
