balanced??

New to these mopar 340's so it might be a stupid question but have to ask.
I have a 340 with a build date of 9-24-71. Would this be internally or externally balanced?? I think it is a forged crank motor. Read some where that they switched over to a cast crank it 72(the motor came out of a 72 challenger) and where externally balanced??. Going to order a convertor for it.
Thanks