Pork for example in the 50s was way, way different than pork today--in the 70s and 80s pork producers decided pork had a bad reputation and bred pigs to be leaner with less fat so it would be sold as healthy food (remember the slogan, 'Pork: the other white meat'?). So if you had pork chops in the 50s they were much fattier and better tasting, almost like steak, vs. what you get today. A tomato meat sauce from that era might have you just use fat pork chunks instead of beef and if you make that same recipe to the letter today you'll just get dry nasty shredded pork.
Another example is jello and aspic. In the 60s jello was new and turned into a fad to make aspic-like dishes, basically meat inside a rich and hearty congealed fat. If you look at cookbooks of that era you'll see all kinds of horrifying things like tuna fish in jello--it was novel at the time but now a curiosity.
Old cookbooks are fun but IMHO I would stick with stuff from recent decades.