Just browsing my Feb jap RC magazine and find some new Kawahara options for MTX4 around mid Jan:
K-863 Alloy side pulley 25T
K-864 Alloy pulley 18T
K-874 One piece alloy engine mount
K-870 MTX4 chassis pro (with cooling opening under engine)
and some other..maybe I should just scan the page since I can't read katagana >_< wellz hope this helps..............