[X] Pull the Lever
Okay, if we're adding organ donations to the mix then we should be maximizing the number of lifesaving donor organs available.
Presumably this one man has five organs that could saved from his trolley mangled corpse (though it's likely some of them would be too damaged to use).
Meanwhile with the five people: If the only thing wrong with them is needing an organ they they all have potentially four donor organs each. Four times five is twenty meaning that by pulling the lever we could potentially be creating enough donor organs to save twenty people.
So, I say we pull the lever. That way the doctors can (potentially) get twenty new donor organs to save more people later instead of just saving five.