Nice, I've been thinking about using 2 or 3 oxygen, Mapp, or propane tanks as a gas tank, I figure I could braze some small steel tube to the sides and connect them with some sort of tube to act as connections. Paint may even be done over though I think I could dig the industrious look of the original tanks, hard to decide...
I've tried the brazing thing it's a unique pain, I've actually seen better success in simply soldering steel pieces together, my metal ammo box I used as a battery and electronics case has an out channel on the side that's just a copper pipe soldered to the steel with silver bearing pipe solder..
I seem to burn holes with brazing on even the simplest things, though maybe it's because I'm always trying on thin metal crap...