There are a few different pros and cons when buying a car that was built 30-40 years ago.
One of the pros is its manifold. Cars that are built today have a plastic manifold. Plastic manifolds deteriorate very fast. Most plastic manifolds will crumble and fall apart after 20 years. And if you have a car from now in twenty years it will be very hard and almost impossible to maintain. Cars from thirty to forty years ago are mostly made with an aluminum or cast iron manifold. Aluminum and cast iron manifolds are very strong and deteriorate at a slower pace. Both aluminum and cast iron manifolds, when well kept, can be maintained for longer than a lifetime. While the manifolds from many years ago are safer and stronger, the ones from now are lighter, meaning better gas mileage.
Another pro is the headlights. Headlights made now are plastic. These plastic headlights are only good for a few years. After even two to five years these headlight caps will be very fogged and stained. When caught early you can remove the stain but this rarely happens. Headlight caps from years ago are more glass. Making it clever at night when you use them. However, Most lights that are made now are LED lights which make it easier to see at night. Led lights are brighter and better then the lights they used many years ago. Even though the lights they used back then are darker and heavier both the light and the headlight are a lot cheaper.