The beltway bridge on the Catonsville line was unspectacular. It was very similar to the WM bridge that was located just west of Reisterstown Road, which was replaced in the late 80's/early 90's when 795 was opened. It was a simple plate girder affair on concrete piers, two sections, painted Public Utility Krypton Enamel (PUKE) green.
Until the most recent lane addition project, the wide jersey wall was still apparent where the center pier once stood. IIRC, it was just south of the Frederick Road exit.
My favorite ghost to chase was the M&P. I especially like the University Parkway bridge, where you can walk along Stoney Run and look up to see soot from old #6 still clinging to the underside of the bridge.
Lee