I have just completed building my XM, new from the ground up. Yep it was stupid expensive for a 2wd, but it looks great! waiting on short servo and new receiver to arrive before running it.
Lee's worlds car is definitely different. looks to be longer in the chassis by about 10mm and a slightly different rear gear box configuration, as explained on Red RC. The rear arms are reversed (left to right and right to left) and sweep forwards. They appear to be 501 arms as well.
To be honest I don't think we'll ever be able to have 'the car' Lee Martin runs. he is always sporting a concept chassis. I wish Lee all the best at the worlds
. It would be great to see a Tamiya TRF take top honours in off road. Maybe then Tamiya might release a worlds special to the same spec??
Regardless, I'm keen to run my XM!