Same '75 duster as my last posts: '76 400 4 bbl w/ holley 4160, Mopar distributor, 727 auto, 8.75" rear end (trans and axle out of the same car as the engine). The diff is open, and feels like it is geared high, like
2.7 or 2.9:1, pretty typical for '76. I would like to go with a limited slip rear with some lower gears, but I need to figure out which gears to go with. when I eventually finish the car and build the engine, I want to be able to outrun a viper in the quarter, but I don't want a car that will redline at 120 mph, since this car will see occasional street and perhaps some highway driving. As near as I can figure, 3.55:1 gearset times the car's 2.45 first gives me a final drive a little lower than the viper's (3.07 axle * 2.66 first) and a top speed approaching 160 assuming a 7000 rpm redline with the tires I am using (Yokohama avid S/T 255 series 27" overall diameter), but the viper has a manual and puts A LOT of power to the ground. I figure with this gearing and the fact that I have an automatic, I will need make between at least 560 lbs-ft. of torque at the flywheel to match the viper's power at the wheels. Is that feasible with this engine, running on pump gas? Would stroking the engine to 451 cubes help at all? Or should I go with lower gears like 3.91s or 4.10s and just deal with the lower top speed and higher rpms at highway speeds? 4.11s with the same tires and 7000 rpm redline would give me about 135 mph, and over 3000 rpm at 60mph. Thanks in advance for your advice!