I built a pump module setup along the lines of a factory unit. It holds the Aeromotive 340 pump, return line and the fuel sender. It's hard to see in the picture, but the return line does double duty as the pump mount also. I made it from 1/2" tubing for extra strength. There is a reinforcing ring welded to the inside of the tank that the module bolts thread into. The gasket in the picture is Neoprene, but that was only used for leak testing since Neoprene isn't compatible with gas. I'll replace it with something else during final assembly. Most likely Viton.
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The small white parts are electrical bulkheads for the fuel pump. These are made from Teflon (PTFE) which is unaffected by gas or alcohol. They're sealed with Viton O-rings. I made them to the same general shape as the B+ connection on a GM alternator. That allows them to use the same insulating boots.
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The tank is built from 5052 aluminum. This is an alloy recommended for aircraft and marine fuel tanks. The aircraft part didn't mean a lot because aviation gas doesn't contain ethanol, but a marine tank will almost certainly see contact with water. I was concerned about corrosion due to fact that ethanol can hold a good bit of water. I try not to use ethanol, but that's just not always possible.
I actually had enough 304 stainless on hand to build the tank, but it was going to be pretty heavy. Since all that weight is behind the axle, I decided to switch to aluminum. However, I am definitely not an accomplished aluminum welder and this tank is the single largest project I've ever done in that material. I pressure tested it with 3 pounds of air and soapy water. I found 3 pinhole leaks that were fairly easy to repair. Considering that it should never see any pressure normally, I think that's good enough. I did add some doubling strips where it lays against the chassis and where the mounting straps lay.
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I noticed after getting it hung that I need to add some reinforcing where the mounting brackets are on the frame. It would be easy to for the steel frame bracket to punch a hole in the tank in an accident.