On the crankshaft flange, the bolt pattern for a flywheel and a flex plate are the same. The manual transmission crankshaft must have a pilot bearing in the center hole of the crank.... on an automatic, it doesnt use the pilot bearing so it doesnt matter. The center flange of a flex plate is thinner than a flywheel. Get new bolts from either the Chev dealer OR a good speed shop. Torque the bolts to the listed spec.

Yes, the converter bolts to the flex plate. Use new Chevy bolts here also.....never use hardware store bolts in either locaton. The bolts are less than a buck each at the Chevy house.

Always run the dust cover on the transmission to cover the flywheel or flexplate at the bottom.