I have a 67 RS/SS BB NOM and have a 12 bolt 3.55 posi gear ratio in the rear. I have a 255 R70 15 inch wheel in the back and I want to replace this with either a 4.10 or 4.11 posi to get the punchy feel. Did either gear ratio exist then, and any suggestions on brands, and what to look out for when having it done. Thanks!!