Mr. Maryn is a Kokomo boy, or was. He left Indiana for grad school right about the time you're concerned with.
He lived in town, his family white-collar. They ate breakfast, lunch, and dinner, although occasionally his grandmother might call that last meal supper. When there was a big meal served mid-day or early afternoon, it was dinner. Christmas dinner, Sunday dinner, like that.
His cousins were the sons of farmers and blue collar. Their parents used breakfast, dinner, supper, but the teens in the house rejected that and used the same terms as Mr. Maryn.
The family kitchen had cabinets, plural, but he'd get something from the cupboard.
His sofa was a couch. An automobile's transmission was a tranny. If I think of other regionalisms, I'll edit them in. Edit: I talked to him about this thread. He said it's a davenport and he only started saying couch because I did.
One thing which may be hard to impart but which was certainly true of older Hoosiers in the 70s was odd pronunciation of certain words. Hawaii was huh-WOY-ee, goofy was just like goody only with the F sound (Mr. Maryn still messes that up occasionally), and dino-sours once roamed the earth.
Maryn, who's still got lots of family in Indiana