5.9 Magnum flywheel - DIY with bolt-on weight??

I have this posted at Mochat. A member there says the flywheel is cast steel not cast iron. If true the weight goes up by 5%.

I could not verify that it is cast steel. Mopar Performance just lists it as "cast" and sells steel flywheels under a different part number. Summit advertises it as steel, does not even say it is cast. JEGS does not use the word steel.

Anyone know?