Thanks for all the responses. To address a few:
I'm planning on building a vertical smoker, no box. Somewhat representative of a Backwoods smoker. Charcoal on the bottom, water pan above, and three racks on top that are spaced enough to hold ribs, or remove the top rack and do a whole hog!
Since I'm using bolts and nuts, I imaging the seams will need extra strips of stock metal bought from home depot...this allows me to connect two sides without bending any metal.
Sounds like burning it out at the beginning will losen up all the cr** inside making it easier to sand off. It'll be inside after that, but maybe I should oil it up during the process? Anyone know of good rust removal products that they've used?