I usually get pork baby back ribs for smoking, but this time my wife bought some center-cut spareribs with the pork brisket, or rib tips, attached. I plan to trim it away and smoke it with the ribs, but separately. Any advice for cutting and cooking? I'm using a Weber Smokey Mountain.

I like finishing them in the oven, in a foil covered disposable foil pan. I do Boston Butt/pulled pork the same way. Cuts down on the final cooking time. They come out fall apart tender after 1.5 - 2 hrs. When I want some bite to them then I skip the oven and finish and sauce them on the gas grill..

Together in the smoker with a deep drip pan. May take a bit longer but worth the wait.

Agree with Sixpak on this.
I'd do them in the oven together till 3/4 done, drain the excess fat off and then slice the ribs off the roast, sauce and grill to finish.

I use to go to a Gasthaus in Germany that served wild boar. They would cut the ribs and and the whole section including the outer skin and slow roast it. You would get a slice of 3-4 ribs that was 3 inches thick.