I'm running a RB 728 in my truggy. I get great fuel economy and I have power for days. In my .5 truggy, I'm running a NSR.12S3 Novarossi. I just love the Novarossi based engine.
Another good engine for not too much money is the Eco .21 series motors. I have seen many guys beat much of the competition with these Novarossi based engines.