I don't know what is considered a 1/8th scale motor. Y do u want a 1/8th scale motor?? in this?
RX8 and a 4.5/5.5t 550 motor is plenty.
I didn't MODIFY anything, i have setups below...
http://www.youtube.com/watch?v=whfUdzwpYgw
or type in "How to fit 550motor in SC10 4x4"
THX