For people who fly this route often:

IAD-LAX UA342 - 777 (used to be 937 didn't it?)

how often is this old config vs. new config? or is it always old config?
(I know the 777 keeps disappearing off this route anyway so I have to imagine when it is on there it is old config?)

edit: in particular I'm looking Sunday Sept 16, edit2: further this is more a curiosity since I will likely book the flight either way more due to schedule than aircraft type anyway - especially since old config 777 is still better than 737 or a320