A special tool is not needed to remove an outside door handle on a ’49 Cadillac. The outside door handles are attached to a 3 or 4 inch long square shaft that is perpendicular to the axis of the handle and which goes into the door. Inside the door, the male shaft goes into a square female hole in the door latch mechanism. This male shaft is held into the female hole by a lock screw that is, in turn, perpendicular to the axis of the shaft. On early ’49s the screw has an ordinary slotted head. On later cars the screw is really a small bolt with a ¼ inch hex head.
Let’s assume it is a front door. (Sedan rear doors should be the same. Can anyone enlighten?) To access the screw/bolt, peel back the rubber weather-strip on the side of the door at a point slightly above the level of the door latch. In doing so, you will uncover a small hole in the door about a ½ inch in diameter.
Shine a flashlight into the hole so you can see the screw head, which is 2 or 3 inches down inside the door. This will reveal whether the screw head requires a screwdriver or a ¼ inch socket. If it requires a ¼ inch socket, the hole is sometimes too narrow in diameter to admit the socket into the hole. If this is the case, enlarge the hole with a file or use a ¼ inch nut driver which has a narrower head than a socket.
With one hand on the door handle, loosen the screw just enough to free the door handle and pull it out of its place. Do not loosen the screw any further, as it may come out of the threads in the door latch and fall to the bottom of the inside of the door. To retrieve it you would have to take apart the door or, if it is a slotted screw, replace it using a magnetic screwdriver, both of which procedures you obviously want to avoid.