Hi Kuretake, just so we can better help, there were two different radios used in the 1949 Kaiser and both mounted very differently so it's important to know which one you have.
One was the early 1947/48 style radio which was installed with an adapter kit. The other is the more common and larger one, with 6 push buttons, which mounts differently.
The top picture is the first style, the second is the other but the pic shows what it looks like mounted in a Frazer but it will look similar. Let us know which one you have.