I've been wanting to do this for awhile now. I've already converted it to natural gas, so that part of the job is done. I was going to go the way of the pilot light like others have documented, but didn't make me comfortable. I have had ALOT of problems with the flame going out on the stock XL burner. A system with a safety valve makes this much safer.
Started by searching for a cheap used gas oven on CL. I founf a 10 yr old GE missing a door for $30. SCORE! Only problem after hooking it up was that the igniter was shot. So out of pocket for another 25. So $55 in and I have all the components to make my smoker 'set and forget'. The system runs on 110V, but my smoker is stationary, and I have outdoor power right next to it. The thermostat should go from 150 to 500. Thats a better low end than you can get on a stock XL for sure.
Decided to use the burner bar for the gas oven as well. Makes for alot less fabrication. So last night I got started by power washing the XL and tearing out the stock burner and components.
Laid out some cut lines on the bottom for where the new burner would live. Got out the cut off and went to town.
I used the stock burner bar mounting hole on the one end and fabbed a steel bracket on the other end. The bar only sticks down 5" or so, so there was plenty of clearance underneath the smoker for all the components to live.
With the burner/valve assembly mounted, It was time to consider a wind break. After a quick check, the stock XL burner mount covered all of the burner holes, So with a quick trim for the igniter, I bolted her back up. I will more than likely trim the height down after I get all of my fitting done before final re-assembly. I also need to address the huge hole in the bottom where all of the un-captured drippings can fall through and stain my deck (even more).
I luckily found a perfectly sized piece of heavy steel channel to use as the burner bar cover. This will give me some mass to help distribute heat evenly, and a place to set the wood chunks for smoking. I will hold onto the cast iron pan for now, but may not be necessary. I am going to install a height adjustment system for the channel so I can keep the wood burning at the right temp, no matter what temp I'm smoking at.