[kiwi_steve]

I don't have one, so this is just an educated guess.

The speaker - which has an unusual large metal frame and is probably specific to this model or a few similar models - is most likely bolted to the chassis where the two clear strips are just behind the indent on the chassis (probably mounted from the magnet area - you can just see one in this photo http://postimg.org/image/zdvzpr5nh/ to the right of the IF can), and the dial assembly is bolted to the top of the speaker.

The speaker is part of the mechanical assembly for the front of the radio, almost like the engine in a motorbike often forms part of the frame... so not having the original one might be a problem. If you do not find an original speaker then you will need to make a suitable bracket(s) to mount everything in the correct place. I suspect those speakers will be very hard to find unless you can find another radio for parts.

Cheers

Steve