Definitely take it from the pump. You'll be surprised at how quick and how little material will be remove to accommodate a 1+" diameter barrel. You take the freak down, and then you have to contend with the finish, etc. Plus, you'll be prepared for any barrel with the pump widened.
Mine is widened with the stock barrel atm. Other than a very little bit of twisting that can be induced while I'm pumping kinda lazy, It's holding up like a champ.