1974 duster factory big block 400 car??????

I can't envision the factory even having the ability to create such a car although a friend ordered a new 1976 Chevy Monza Town Coupe with a 350 4 gear and it came through. Had a weak Saginaw 4 speed and tiny rear end. Thing flew until he blew both the trans and rear end. Dealer fixed it once under warranty but told him no more repairs because RPO cars don't have warranties.