OK, thanks for the tip. Don't worry, I have no intention of wrecking it - the refurb'd Scorcher is not likely to be run anyway - I have other cars to bash around with. This Scorcher is really just sentimental as I've owned it for 25 years.
The diff. was an upgrade I bought a couple of years after buying the car to try and fix that terrible understeer. I immediately disassembled it because at that time (aged 14) I had no idea how such things worked (and a curious mind!). For what it's worth, looking at the thread linked to above regarding taking it apart, mine just pulled apart - no tools required. I remember doing that and being seriously impressed with the quality of engineering.
I bought a few hop up parts for the Scorcher around that time - a steel bumper and stainless steel UJ's from Green Models (or whatever he was called back then), Acoms electronic speed control (that kept burning out transistors on a farily regular basis). A few other bits (actually, looking back it was quite a tricked out car given that I was never a racer).
What this thread has convinced me to do is to restore the Scorcher complete with the period hop-ups. Originally I thought I'd restore it to box stock which was, of course, how I originally built it. But really these upgraded parts are all part of the cars history (and mine too) and should rightfully stay in it.