I would think they'd be running a 7-car set. 7 is the longest Harrison can handle IIRC.
"This is an Raritan Valley express train to Allentown stopping at Newark Penn Station, Westfield, Plainfield, Bridgewater, Somerville, Raritan, High Bridge, Philipsburg, Easton, Bethlehem, and Allentown. Transfer at Newark for service to West Trenton and Lakehurst. Next stop is Newark."