Drive shaft

According to the chart, it looks like your original car came with a 3.25" diameter shaft. This is beefier than a 3" shaft and will handle more torque and HP. But Mopar also used a 3.0" on a 340 Duster with an 8.75. IMO, unless you've got a monster HP engine or you use it for drag racing, the 3" driveshaft should be okay.