Be sure to research the right replacement part for your application. An improperly balanced rotating assembly will wreak havoc on the rest of your motor.
In addition to the flywheel and flexplate, you’ll need a new ring gear plate, flywheel/flex plate bolts (optional), loctite.
New GM flywheels can be purchased from Eckler’s. It’s a good idea to save your old plate so you can match it up to the new one.
Flexplates are visibly different than flywheels. There is no machined surface required for a clutch. The torque converter bolts right up to the center of the plate and transfers the power to the transmission.