TCX wishbones, hubs, shocks, bearings and diffs all fit.
TCX belts and complete layshaft/pulleys can be fitted (you have to change the whole lot as the pulleys are bigger so need the longer belts).
Driveshafts don't fit as the TCX ones are longer and a different (crap) design.
Your best bet for driveshafts are these:
http://cgi.ebay.co.uk/3Racing-CY-33-...item588b888753
They're 100% steel so are much more durable than the purple alloy ones. We've had a set on the front with a spool for 12 months and no real signs of play.
Either that or look out for some old HPI Pro4 driveshafts on ebay; the bones will be too long, but the axles are the same.