I'm not too familiar with Torresdale and the nearby area, but one decent place is at 30th Street station. Aside from all the various passenger trains, the elevated "High Line" next to it (around 31s Street) has fairly frequent freight. I've never been there, but the CSX tracks along the Schuylkill River by the bike path might be a good place as well.
My personal favorite place is the old Port Kennedy station in Valley Forge Park off of Rt 23. Lots of freight trains there, although it's probably too far. If you're ever out that way though, it's worth a stop.
The picture to the right is a photo of Silverliner I 246 located at the Railroad Museum of Pennsylvania in Strasburg, PA.