FWIW, I saw it yesterday around 9:30pm ET. Debated doing SDC as there was on RUC seat available on an earlier flight, but was worried that in the 45 minute hold time for an agent it could disappear, and there weren't any good Y/C+ seats.
RUCs for flights with "First Class" seems to map to Z inventory, which you can see in the search results grid, although if there are no Z fares meeting the A/P requirements depending on your flight date, then you'd have to use something like ExpertFlyer.
Not sure exactly how anything to DeltaOne works for either RUC or GUC.