Seeing the demise of the STL-LAX $200 fare this is the next best thing I see on ITA for double elite mile seekers from St. Louis.

Don't have time to look further on this now, but it seems the DL fare has more availability then AA, and it is easier to maximize the miles on Delta.

There's also a fare to GEG for about $255 ai that might be used to pile up more miles. Again, AA seems to have less availability.