Of course I was being a smart ass...but only a little so get over it and try don't take yourself so serious amigo!
The fact is, it's foolishly simple to take one piece of tin and change the add-on things like color, graphics, emblems, gas caps etc and reuse the piece. Could be from the same or similar models sold in different markets. Here's one for you that is directly related to tanks; I have two Yamaha XS750 US tanks here on the shelf (it's a beautiful tank for a cafe by the way) both from standard models, both 750, one is a 76 and one is a 77. Guess what? One has a screw on plastic emblem on each side, one has decals but that's the only difference.
Wacky stuff huh?
As for your original question; there's only a few ways tanks are mounted to a bike and generally swapping is just a matter of making one mounting system or another work between the two (tank vs. bike). Heck you could strap mount it with a cool old leather belt and really rock the old school. I've been eyeballing one of those XS tanks and am strongly considering adding a 'groove' in the sheetmetal and moving the fill neck off to the side so I can add a stainless strap to mount it on a bike I'm thinking about building. How you mount the tank is up to you my friend, knock yourself out! (just fall somewhere soft...)