How can I get into my 1940 60 Special Fleetwood with both front doors locked and the key is not unlocking them?
I don't think it is wise to ask on a public forum how to break into a car. Call a locksmith.
A '40 Cadillac might possibly be gotten into with what is called a "slim Jim". I have one (my daughter locked her keys in her car on occasion), probably most any locksmith would have one. In our "little" town the sheriff's dept. will sometimes send out a volunteer deputy with a slim Jim and unlock your car for you, if a volunteer is available.