Thanks to FSDan for the inspiration, and also from requests of others on his threads. I have decided to add WN to the list for Thursday, July 26th. Unfortunately, I didn't exactly divide out the 733/735/73G/738. This is moreover just an updated count of their flight count (On the SWA website, latest data is of Feb). Seeing how there is no difference in seat count between the 733/73G (the majority of the fleet), the retiring of the 735, the slow addition of the 738, the overall average should still come out to be close/near the original seat count of 137.
I included SAN/STL because I thought they would be close to the ~100 threshold but didn't exactly know where they would stand out until I completed the counts.