5.7 L Hemi, ZF 8HP70 Swap

8 speed would be great a 5 or 6 speed auto would get you there. The 6 speed manual in my Challenger is a double o/d and tach's about 2500 r's @100 mph. Steady 25 mpg. @ 75. Overdrive with the correctly matched rear gear and rear tire size makes quick off the line and good mileage both a reality. tmm