I have been looking at this motor: http://www2.towerhobbies.com/cgi-bin...&I=LXGGP7&P=ML

I think it is a direct drop in with no modifications. There is an (S) version that has a longer shaft, but I think this is the one you want. I am sure someone knows for sure which one you want. I am thinking about buying one for my MT2 (working my way up to a .28). Also, there is a .18 upgrade you can do to the stock NT-16 motor. That info is here: http://www.rcuniverse.com/forum/m_2520395/tm.htm

I just did this upgrade on my son's ATX and it is a noticeable difference. But probably not as powerful as the OS .18 CV-RX. Hope this helps.