Help with 55 Gallon offset project

[Phinnay]

Hey! Been reading this forum for quite some time and looking to upgrade from my cheapie square Brinkmann smoker.

Got the idea to build a small offset out of a 55 gallon drum I have the tools and the drum but I am unsure what to do about a firebox.

Ive thought of using a Grill sized propane tank on its side for a firebox but I'm not sure if this will be big enough. I considered a beer keg too but then we get into welding aluminum to steel .

Any ideas? I'm tryin to avoid weldin up one myself because I dont have a sheet roller. Seems silly to pay n have someone else fabricate me up something when I could use what I got layin around.

Thanks!!!!!