This is a vintage OEM GM manual transmission flywheel for internally balanced Small and Big Block Chevy engines. This flywheel is the larger diameter version with 168 teeth on the ring gear. This style used the larger 11 inch clutch disc from the factory and is known for factory high performance and many Big Block Chevy applications. This will fit all internally balanced Small and Big Block Chevy engines from 1955-1986. This includes 265, 283, 302, 327, 350, 396, and 427 engines. Please confirm your specific application based on the casting number and ring gear size. The casting number is 3973456N as shown. The N means its nodular iron which is the stronger, heavy duty factory piece. The date code is L 1 8 which decodes as December 1st, 1968(or 1978?).  Like other classic car drivetrain components, the parts need to be the correct part number and date in order to be considered number's matching. Items like flywheels did not used to be looked at as important in regards to part numbers and date codes. As the hobby has progressed, parts like this flywheel are considered part of the package in order for a vehicle to be full number's matching. Don't miss this real deal original example.