I have a 1970 Z28 with the Sawginaw 5691676/ (4 bolt unit but only use's 3 bolts) steering gearbox on it. According to spec data the optional power steering on the 1970 Zs came as a variable ratio at 14.3-10.9:1 for 2.3 turns lock to lock. I sent my gearbox to Lee power steering in Valencia, Ca for a complete rebuild and to verify the ratio. I was notified that my gearbox was not rebuildable and the they could build me a new 3 bolt gearbox that would be a straight 12-1 ratio. Does anyone know if this sounds right or what the difference is.