I need to have my 440 cast crank rotating assembly balanced because I am replacing rods and pistons.When balancing an externally balanced engine will the machine shop need the torque converter as well as the harmonic balancer and flex plate?Also, if this is done can I get rid of the external balance weights and treat it like a forged crank assembly?Does anyone have the specs on how out of balance the stock rotating cast assembly is supposed to be?Thanks...desperately need some good answers!

If you use the B&M plate w/ the weight notched out, you can then use a neutral balance converter.
To balance it they'll need the balancer and flexplate. If you want to continue using the stock flexplate and weighted converter, take them the converter also.

Bring the balancer, flex plate and converter, but if you're using lighter parts, it's probable that it CAN be internally balanced. If the balancer and flex plate/etc are bias weighted, you will need to buy neutral parts if you want it internal. S/F....Ken M