That's not a butt. That's part of a butt, and I'd wrap in foil to better hold moisture once the bark looks good. If you're tracking the meat's temp, 160* might be about right. Be forwarned. Those little shoulder portions can take a lot longer than you'd think, so just chop if it's not tender enough to pull before your people revolt. So what's "tender enough to pull?" Well, it's really a misnomer, because the meat should just about fall apart on it's own. You should be pulling the roast apart, but not having to pull the meat into shreds. Thumb-sized chunks is optimum, but if you don't cook to this tenderness, that's ok. Just chop it. That's what they do in the Carolina's anyway.