Before you remove the third member from your car go buy a factory service manual for the car, all Mopar cars that came with 8 3/4 stareted using the "489" third mebers in them so make sure the manual you purchase covers those years from 1969 to 1974 Read (and understand all the terms as well as the procedures ) the section on how to prepare that third member and the tools needed( pinion depth seting tool. dial indicator with a good magnetic base, inch lb torque wrench, 250 Ft lbs torque wrench, proper size spanner wrench) and so on to set those type gears( 1 7/8 inch tapered pinion gears with a crush sleeve) up correctly, if you want to continue then buy all the tools needed and have fun