Silver solder ought to work, less heat.
I tried silver brazing on a stainless tank. It made cracks, severly. Junked it. Seems some stainless's don't like to be 1200 degrees. So, being an unknown alloy, next time I'll try solder. It's lead free, takes umm 600 degrees? Solder form the inside, to make sure no cracks to harbor germs?
How wide is the bottom? Needs lots of area to get the heat to 10 gallons, but I suppose that the fiver is broader than the burner anyhow.