My 55.2 has 3.55s in it, installed by previous owner. With that and 30" rear tires it cruises comfortably at 62 mph. It will run faster, but I don't feel the need to push it. It's running about 2500 rpm, near torque peak.

Devin

If you can't hose it out it ain't a truck

55 3100
63 Corvair Monza
64 El Camino
72 240Z
01 Suburban