I'm getting ready to overhaul a radio that dates from roughly 1954 and am
wondering which kinds of capacitors need replacing.

I know the electrolytics and wax-paper capacitors (with wax outer surfaces)
need replacing, and the mica and ceramic ones don't. (One of the
electrolytics has failed, which is what got me started on the project.)

What about the ones housed in plastic tubes (with a hard plastic surface)?
Are they wax and paper or are they plastic inside?