Learn me custom fuel tank

I need a fuel tank for the Rice Rod. Though it's slightly beyond Challenge budget, I am still keeping it cheap. I want to re-use the donor car's sender and in-tank EFI pump, since they're free, I know they work, and they're designed for this engine and gauge cluster (yeah I'm keeping that too). I'm going to weld a simple pump mount to the sender flange, drill holes in the sender flange and use bulkhead AN fittings for fuel supply and return lines. The AN fittings mean I can easily upgrade fuel pump in the future, you know, in case of turbo.

I am liking what this guy did, but with a custom tank, and hard lines instead of braided hose:

This way I only have 2 holes in the tank- sender/pump/lines flange and the filler/cap. This means I can use pretty much any tank. Now I just need a tank.

It needs to fit in a 12x12x20 space, which is about 11 gallons, so it rules out many off-the-shelf tanks, which are too pricey anyway.

• Should I use steel or aluminum? I can weld both. Aluminum will look like a simple dumb box and be thick (1/8" min is what I'm finding). Steel will require me to buy a bead roller, and could potentially look more "hot rod". Also probably cheaper.
• If I use steel, what thickness?
• If I use steel, does the inside need some sort of coating? Can I just paint the outside and call it done?
• What about venting? How do I do that, or do I even need to?
• How do I make flange holes on my tank? Drill press and taps?
• What else am I missing here?

The team gutty guys found x2 stainless steel sinks of similar dimensions and welded them together. Stainless would eliminate many of your concerns above. 

Start with an empty keg?

I built one out of steel for my Seven. It had pinhole leaks in the MIG welds. I gave it the Kreem treatment which sealed it and protected it from rust - you can get it from motorcycle shops. I'd probably do aluminum if I did it again, TIG should be easier to plug up.

You'll want venting. Get that from your donor tank.

Flange holes? You mean something to bolt that whole sender/pump/float assembly to? I'd weld nuts to the inside of the tank.

Oh my gosh!

I might have something sweet for you. This came on the 'fiat-in-a-field' car, and hard to tell in the pics but its date of manufacture says 1-1978. It was made for a fuel bag inside I think, but if you can use it its yours (or trade me for an equivalent weight of metal pieces that might be useful to the fiat challenge build). I can measure it tonight.

Kinda leaning towards simple aluminum box now. It will take less time and new tools, won't look as "old-school", but it's also hidden under the truck bed between the frame rails, so you won't see it anyway. Let me know what you find Robbie. It can't be wider than 12" or else the lower links and driveshaft get uncomfortably close. 

In reply to maschinenbau :

I'm using a polished aluminum square cell I found on ebay new for $73.  Well constructed and has foam and a prewired gauge sender.  Woul need mod for in tank pump.

Stainless sheet (0.032" thick) with end caps flanged to the outside for easy welding. Add internal baffles (baffles will help maintain shape when there is a pressure buildup in the tank) or plan to make the cover plate hole big enough to add fuel cell foam. Carbon steel WILL rust if not coated internally. Aluminum MAY oxidize in the presence of the alcohol in the fuel. Stainless will last forever.

I had to make one for my spitfire project and I used PEM nuts for the fill/vent/inlet/outlet cover plate attachment bolts, along with gaskets to seal everything. I leak checked with water and a few psi of air pressure. no problems and the shop never smells of gas that a pinhole leak will generate.

I didn't have a tape measure handy, so I used the always-accurate "hand and eyeball" method. It's about 9x12x18. 

The whole side comes off, so if you made an aluminum tank you could slide it inside this one, but it might be a little small for what you want. It would seem it only has about 2/3rds the volume of your space, which you may not want to give up.