I run the 4.5 Orion in my FTSC10 on mmp. I don't think the motor will have the power your looking for! I run a 18t pinion and the big spur. It's super smooth power delivery and really fast on 2s 35c reedy. The esc/motor temps at 100f after 15min plus.
I probably wouldn't run it in a 4x4 though because I think it's more of a onroad motor. The only real way to know is try it out and temp check often.

I'm sure a rs pro would work but you would limit your self on gearing options to keep the heat down like a 9 tooth and then you would be slow. But with a rx8 you could pretty much gear to the moon and be fine!