Welcome from N FLA. That's factory A/C for A body. If you slide under car on driver side you should see engine size cast in block. Sure grip is term for rear end, Posi is GM term. Nice car by the way! Enjoy.
Welcome from one cuda owner to another. One day I hope mine looks as good as yours. My granddaughter has already called dibs on it I hope to finish and drive it before she tries to run off with it lol. I wish my granddaughter lived a little closer so she could be involved in the build like you.