Gas tanks

[WerbyFord]

Ah, so you need a CAR tank!
Those are way more common.'
FYI, 63-64 tank is the same but the FILLER NECK is different so they don't really interchange without a lot of work & welding.
One filler neck has a little more arc than the other or something, so it looks right UNTIL you install it.

So if they tell you 63-64 "fits all" be wary, you don't know which one you're getting.

Lots of 63-64 gas tanks here, I sold a couple used for $25 or something from my dad's parts house. No room to keep them.

[Heo]

I Borrowed a -65 Mustang tank and testfitted, fits fine
It is wider than the galaxie tank but nothing in the way
at the sides. It is shorter lengthwise i just make new bands
and make a new attachment point and make a new fillerneck.
The Mustang has just a short stub for the filler hose so i weld
on a new neck on that
The 69 tank is one inch thicker above the seam and 20 gallons like the Galaxie
And they have stainless tanks in stock in Sweden, for half the price
a non stainless Galaxie tank would cost me with all the fees.

[Ranch]

Does your spare go under the floor over the gas tank. If you have a sub floor it could be the reason for the different shape.  Try buying a '58' Ranchero gas tank, not cheap either but standard would never fit with out cutting the car, aaahh no thank you.

[Heo]

No the spare is in the trunk the tank hangs under the floor
The Mustang tank fits fine, the cheapest tank available and
available in stainless 
Only negative with Mustang tank is maybe it is slightly more
visible from behind