My 47 Buick 56C needs a taller gear to make her happy @ 60- 70 MPH SPEEDS necessary for traveling in todays highway traffic. I did some preliminary research, and it seems there is a 3.90 -1 ratio Buick had available in the late 40's early 50's. Can anyone confirm this and further inform me as to which models and years I need to look for? I am a automotive Technician/Mechanic by profession so I am able to deal with just changing the center section out (preferred) or changing the ring and pinion should anyone have somthing to offer for sale. Any help in this matter will be most appreciated. Jeff