Not all the RV 440's were external balanced with six pack rods though. My '74 is factory internal with regular rods and a cast crank. Had to take mine out to get the hole drilled in the back for a 4 speed.
73 was the last year for the forged crank and the six pack rods....also the torque convertor had a weight welded to it...I was told this was done to make up for the weight of the rods...I don't know if this is true....8)