This 1969 Chevelle SS had already been through a full restoration before the V8 Speed & Resto Shop crew tackled its next upgrade: a Tremec TKO 600 five-speed overdrive conversion behind its 454 big-block, rated to handle 600 pound-feet of torque. The install keeps the shifter in its factory location and drops highway RPM dramatically, a detail one viewer calculated out to roughly 1,750 rpm at 60 mph. Watch the full install to see what it takes to give a numbers-matching muscle car an overdrive gear Detroit never offered.