Did you check to see if you could unbolt the firebox? If it is not welded on, it has to be attached some how. Even if you have to cut the bolts off, you can get new one and bolt the firebox into the correct position. Sounds like you need to turn the box 180 degrees to get it into the correct position. When you put the firebox back on is when you should put the high temp silicon to seal the gap if there is still one.
Team: Pyle's BBQ; Yoder YS640; Good-One "Trail Boss" 60T; Homemade rig; 22" Weber Kettle w/rotisserie ring; Big A$$ Rotisserie; BGE-Small; Weber Kettle Gold, Weber OTS, New Braunfels offset smoker.
Saddles BBQ Bistro