Building a Smoker from a Wood fireplace insert

Ok so I have been thinking for long time about building my own smoker/grill in my backyard.  I have a number of needs that makes this project somewhat unique. I have access to some older fireplace wood inserts that I know others have used for smoking. If anyone has seen or used on of these I would love to see it.  I am trying to get the FB set up below the CC if at all possible.  Once I get the final measurements of the CC I am using I will post a diagram of what I am thinking so I can minimize my mistakes.