I think cast cranks started in 74 but some 74's were still steel (6 pack maybe?). Not sure the difference between the 6 pack dampeners & regular steel crank dampeners but I'd say likely a PO had swapped in a good steel crank 440. Good score!. Here's a BTT & others may clarify further. EDIT this jogged my memory & I had a 73 fury cop car that had a six pack rods 440 & it was orange & I think all 70-73 orange 440's had six pack rods. If yours is OE turquoise then very likely you have a regular steel crank 440