||Twin I beam was intro,d in 1965 in the pick up line. Really not a good light duty design. Hard for a car dealer to set the camber and caster. They could do the toe but they had to heat and bend the beams to do caster. Also once the springs sagged the wheels leaned in at the top. The proper fix was new springs or heat and bend the beams to allow for the sag. The system seemed to fare much better in the larger trucks as most owners went to a truck alignment shop for alignment. The truck shops did a great job as they had the equipment to heat and bend the beams. Ford eventually, I am not sure what year but it was towards the tail end of the twin I beam,s career designed into the system a camber adjustment. For my money the GM style control arm suspension is a far better system in light duty vehicles. My thinking changes when one talks heavy machines, there the solid axle wins.