The crank is from a '72 donor engine with minor polishing. Though allSlant Six cranks produced between 1960 and 1976 are beefy forgings,those from 1968 and later feature a 2.160 diameter flywheel/flexplateregister that accepts commonly available torque converters andflywheels. The pre-'68 register is smaller (1.960 diameter) and must usehard-to-find corresponding transmission components. All forged cranksare neutrally balanced, so mixing production parts rarely causesproblems. Cranks manufactured in 1977 and later are made of cast-nodulariron and have narrow main and rod bearings. Cylinder blocks, cranks,rods, and bearings from 1977 and later engines will not interchange withearlier Slant Sixes.