There were some cars with crumple zones back then, but you very likely do not have a crumple zone capable of protecting you. No matter how long your bonnet, you will probably take the brunt of the impact with your body in a car from the 70s.
Not saying don't drive it, I drive a 90s car with no airbags as a daily so I am only marginally better off.
What ever other car hit will so. In such an accident, the combined crumble zone is halved so. If you a concrete wall, good luck so.
I know what would happen if I have a serious accident in my week-end hobby car so. A likely hood that is significantly reduced by current fuel prices. And a serious maintenance backlog...