My guess is from Pt. Richmond, up the ramp on the South side of the Pr. Richmond branch along Lehigh Ave. to North on the Trenton Ave. Elevated to Frankford Jct. Back around the curve on the NorthEast Corridor Track 1 past Shore Tower, then forward past the tower again onto the Delaware River Railroad & Bridge Company's railroad leading to the Delaware River Railroad & Bridge Company's bridge to Delair, right around the curve at Jersey Tower onto the Camden & Amboy to Pavonia and beyond via Center Tower to Bulson St.
Another way would be Pt. Richmond branch to West Falls, then Belmont and the Junction RR. past Zoo Tower onto the West Philadelphia Elevated RR "High Line". Run around the train, the High Line was double track back then, and go back past Zoo Tower North on the NorthEast Corridor to Shore Tower, Delair, etc.
Physically possible, but not as late as 1969, Pt. Richmond branch to Fairhill Jct., Fairhill branch to Erie Ave., get onto the Newtown branch there, then immediately back onto the connection across the intersection of Erie & Sedgely Aves. onto Track 5 of the NorthEast Corridor. Pull forward across all of the corridor tracks and head for Shore Tower, Delair, etc.
Why not just use a car float from Pt. Richmond?