I had a 30.5 non ported in my 5b then went to a dog pile racing 26 and god damn with this thing rev to the moon! I can outrun the larger motors in my area on a rear Dom,they get me a little in the beginning but I fly by about half way. Not sure if that's the motor You would want In a big 4x4 though as the torque is probably more important than revs. Dog pile also sells a 29.5 that revs like crazy also,haven't tried it though.