340 questions

Sometime in mid to late '72 they changed to the externally-balanced/cast crank/lower compression motors. So, a '72 could be either way depending on date of manufacture, and possibly by assembly plant.
A better pic of the crank would help determine if it's cast or forged. The balancer would also be a dead giveaway, as the cast crank unit is plainly labeled as such.
If its the correct balancer for the crank. I've been mistaken that way once. Cast balancer on a forged crank.