Costco had them-Swift's Premium labeled as St. Louis. $2.39 lb is a deal. However, in picking them out, not all the packages of 3 racks were the same trim. Some still had some of the chine and riblets aboard. Finally found a nice trimmed set at about 3.2 lbs apiece. Just for the record, I don't mind prepping and cooking untrimmed spares either, but there are just two of us and we prefer the St. L. One rack will be more than enough for us. Talking about how to cook on another thread got me hungry for them.
I do believe however, that if the package says St. Louis Style, then by golly they should be trimmed that way. Some folks like to trim them themselves so they can cook along with the ribs and use as riblets or tidbits before supper.
Will consider doing them per Bentley at 275* for 3 hrs and report results when it happens.