318 magnum vibration.

They are just interchanging terminology. Magnums all used the size designation in liters, so 5.2 Magnum is 318 cubic inch Magnum and 5.9 Magnum is 360 cubic inch Magnum.
Balanced parts, like harmonic balancers, flex plates or flywheels, and cranks, roads, and pistons are specific to each family of engine, unless the parts are balanced properly before use.

Edited to remove LA engine from last paragraph.