I pulled my broadcast sheet to see if it would enlighten me or give us a clue as to your question.
It shows the Rear Defroster, Rear Speakers, and Collapsible spare as individual options.(H31,R31,W34)
You would think that if the Rear defroster required the collapsible spare that it would be part of a "package" ie one option requiring the other?
What I can't figure out is that my speaker code R31(1) I believe translates to Rear Mono Speaker, yet I have the R22 Am 8 track stereo option as well. I also have the rear fader which is not listed on the sheet (maybe comes with the 8 track option?) I wonder if they include the other speaker with the defroster option.
I know this doesn't answer your question, but throwing it out in the information pool.
Maybe someone who has a broadcast sheet with the defroster option that had 14" wheels can shed further light.