I have wanted a wood fired out door Pizza Oven for some time now. After considering several different designs I settled in on the Aprovecho Research Center design. I liked it for what I mistakenly felt was an easy design that would be easy to build. Here is a link showing the basic design, http://www.youtube.com/watch?v=z-g3jwv3R8Q They even posted a drawing of the unit and the basics of how to put it together. On the web sight look at publications, then go to about the 4th one about Pizza Ovens with chimneys. There are a number of ovens discussed in the article. Along about page 17 you will find the drawing of the oven. Turns out it is not to scale.
http://www.aprovecho.org/lab/index.php
Here is another video showing one of the ovens in operation.
http://www.youtube.com/watch?v=_s2XZKA3R_8
I found a mechanic that had several barrels sitting out back in the weeds. Turns out he didn't really need them and offered them to me for FREE. Since the price was right I took them. My neighbor and I took his Pick Up Truck into town and picked up 4 barrels, 3 were 55 gal, one was a bit smaller.