Re: Drum SmokerChad, sounds like you got a plan. If you season the inside of the drum, that and use will take care of the inside and keep it from rusting, I think. Before I used mine for the first time, I had it sand blasted (mine spent years of service as a water tank) and then seasoned it with pork lard. It now has a very glossy black finish that is very hard. You can rub your finger accross it and not get even a trace of black on it. Even after pressure washing, and leaving with a tiny bit of water in the bottom, no rust. I wish I could get the outside with this same finish.
Yesterday, I was going to suggest hacking the ends off a propane tank, but didn't because of the weight. I know where there are several propane tanks with some damage to the ends from being moved around with dozers. You'd be surprised at how much weight you can move around with a cheap 2 wheel hand truck.
Just rambling thoughts here. If you need any help, let me know.