Thought I'd post a bit of an update on the progress of the Wayback Machine.
The Wifi connection is working using the Wifly module (see previous post) and connects nicely to the router. I've had a few problems with RFI where the signal from the built in antenna seems to interfere with the other electronics causing the Wifly to keep resetting until you stop it by touching (and attenuating) the antenna with your finger. I hope to solve this at some point.
I made a start stripping down the old Hacker radio. I thought I might be able to resuse the amplifier board, but to be honest I don't think I'm going to have room for all the electronics and two PP9 batteries too. So I'm hoping the Waveshield amp is capable of driving the speaker, perhaps with a small amp.
Next step is to get the Arduinos wired up together and to the Wifly via a MAX3232. (The Wifly is 3.3V logic, so needs a level converter and the MAX is a very proper way of doing that.)
I've also got to get the hacksaw out at some point and make a new Perspex front panel.
Still lots to do...