Smoking Pork Shoulder and Pork Spare Ribs Together

I've done it...all you need to do is know when you want everything done and backwards plan.  I plan 2 hrs per lb on a butt so 10 hours prior to meal time put the butt on.  Some use 1.5 hrs per lb for butt but I like to use 2 for a fudge factor.  If it's done early, you can hold it in a cambro (aka wrap the butt in foil then wrapped it in a towel and put it in a beer cooler.  I like 3-2-1 ribs so 4 hrs later (6 hrs prior to meal time) I put the ribs on.  Don't forget to add time for cooker start up and after the cook prep. I plan about an hour sor so for both (start the cooker about 11.5 to 12 hours prior to meal time).

Yes, both can cook at the same temp, 225* - 240*. 

This will explain the 3-2-1 ribs that Bama mentioned, very popular way to smoke them and almost guaranteed great results:

http://www.smoking-meat.com/july-12-2012-221-baby-back-ribs-on-big-green-egg-ceramic-cooker.html