South Bend will tell you the same mis-information about the flywheels. Listen to the engine balancer. That's all they do for a living, they know the difference between neutral and exteranally balanced. The shop that balanced my 6.9 told me the exact same thing......... 6.9 and 7.3 IDI are NOT externally balanced engines.
By the way, that is the same flywheel casting that I got from South Bend....... As I have said before, lots of clutch companies use that flywheel with their SMF kits. Sucks too as they can't control the qauality of that flywheel.
Heath