I think mine is an older big brother to your score and just yesterday started measuring an sketching a remodel from a gasser to a charcoal/stickburner. Mine is a "Grand Hall" made in China for Sam's Club, marketed as a MembersMark product. I cooked on it for about 10 years and got pretty good results but since I build my reverse flow a couple years ago, I've just had it mounted to the trailer and used is as an oven, but I think it will make a nice insulated vertical. The top cooking chamber is already insulated.
The bottom chamber is not insulated but it is plenty big to let me add 2" of insulation and a 1/4" firebox, charcoal grate, etc. (I've been using the lower chamber to store my gas frier & stuff)
My plan is to keep the water pan but gut the wood chip drawers and burner & controls.
I'm thinking I'll be able to preserve the SS exterior pretty much in tact. Good luck on your build and I'll be watchin closely to try and learn something.