forged steel was used until 72 sometime in 72 they started using cast cranks , now i have taken the pan off and have confirmed that it is a cast crank, i can get the right flywheel for it from napa but it will take 3-4 weeks to get one in so i was hoping i can find one that i can get quickerI believe all the '72-'73 340 four speed cars had forged cranks in them. Not sure if one was ever made. The ballance factor is in the mopar engines book so a good machine shop could probably convert an internal ballance flywheel to the specs you need for your 340.