I can't believe you have a tiny 3.3 in a mammoth...
Although, pretty sure I saw a video once where a guy put the losi 3.4 in an LST. Just have to really gear it down... or run small tires!
What I do know is that it's geared a little tall and the shock towers bend easily.
The XTM 24.7 is a good engine though, and after doubling up the shock towers or getting a good roll cage (rc-solutions), that problem will go away or at least be less of an issue. But, it will be still geared...