hi the 70-71hp or hp2 440 6bbl 0r 4bbl are externally balanced . That's why on an automatic car there are weights on the torque converter and on a 4speed car it has a 10.5 inch flywheel with holes drilled in it.
In '72-'75 the hp motors are neutrally balanced-they don't have any external balancing systems. Which is why it has a thin balancer on it.