Thanks for all of the input, I'm glad to hear that people have used AC tanks with great success. However, I found out today that it's only an 80 gallon tank (one of the guys in the shop that has the tank overestimated it's size and another guy gave me the real scoop). I was hoping to build a trailer cooker, but now this just gives me an excuse to look for something much larger for the trailer. I think I'll still grab the 80 gallon tank as it'll make an awesome backyard cooker.
Steve, those are great pics. Looks like you made an awesome cooker!
seattlepitboss, I will be following your build thread, looks like you're off to a great start!