i converted mine to accept the savage axles and tires , you will need to change the hub bearing and some savage axles i think. that will solve axles from bending, the 21 motor is the only one that will fit unless you make some new holes in the chassi . i had a 24 .7 in mine and it was alot faster but the mounts just kept moving and in the end retired it last year but used all the parts to make a crawler. i also think the xtm diffs may fit also because they are also straight gears, dont know about the torer terror but look the same. the cb are all the same pitch so i would think that any 2 speed cb will fit.