Try a 12 bolt posi maybe 3.73 gears or so . Try Jegs or Summit if you want . You could probablly find a used one out a Z-28 and re- condition it. I like Crane Cams Extreme Energy Cams they have a broad torque range. Try not to over cam the 454 . 268- 272 duration is plenty for the street. Low end torque is where the big blocks really take over!!!!