Far as I can tell, my 55T's came set at 0 degrees. You can tell because the timing mark (endbell screws) is aligned exactly between the magnets, which also happens to be right in the middle of the two motor mount screws on the other end of the can.
It is true that advancing the timing will give higher RPM, but remember with a clod that one of the motors will need to be turned the oppisite direction due to the reverse rotation, or you will actually lose performace by retarding the timing on that motor.
Also be aware that advancing the timing to extremes (30+ degrees) will give a ton of performance, but will also kill the motor. 34 degree stock class motors drove a lot of people away from racing in the 90's because they only lasted a week or two before they died. They were sealed back then, and could not be rebuilt.
Playing with the timing is actually something I've been wondering about if I run into problems with "Clod stall". Lots of people run different sized pinions, but I was considering playing with timing. Not really an issue for me now with the 2.2's, but sonner or later I'm gonna mount up a set of LST tires, and I'm guessing it will be more noticable then.