Theron--
Assuming you are cooking a regular butt, the ribs will take considerably less time. Start the butt on the upper grate and when you're ready to start the ribs move the butt to the lower grate and cook the ribs on top which will allow easier access. Time it so that the butt will be done sometime around the ribs' halfway point (don't go nuts with this; close enough is good enough and you have plenty of leeway since you'll want to rest the butts a while). A bit before the ribs are done, unwrap the rested butt and pull it; keep warm. Finish the ribs, serve all, enjoy. Have fun with it.