IMO the 26 is just to small for the heavy revo. Id go 28 for bashing! 26 might be ok on a really tight track I've seen it done but the rpm's sign off to quick and if you gear higher I think acceleration suffers and temps rise quick. With the 28 you will have monster power on tap at all times. Another good cheap motor I like in the revo is the axial 28rr, these things really rip for less money!
You can get the traxxas big block motor mount for around $35 if you look around.