Yep what Corky said, do a reverse sear. Indirect in smoke(red oak is a must for Santa Maria style) until 120ish, then move to direct heat and sear until crust forms. I prefer Rub Company Santa Maria rub myself, but you can't go wrong with an Oakridge product. Good luck and don't forget to post some pr0n!
22 WSM, XL BGE, Weber Kettle, Mini WSM, Blackstone pizza oven