Hey guys, Need some help!

My brother got a 74 Chevy Nova, and we were wondering what parts can we change. Like the front-end, can we put a 72 or 70 grille, lights, and bumper on or are we going to have to the whole front-end. The interior can we put 72 door panels to carpet to headliner in or we have to find 74 interior parts. Thanks for the help.