I can tell you from experience, especially being a heavier ride (220), that even a ported 310 will not allow you to run off and leave the 450's. I ran a ported 310pv for the last 2 years. It allowed me to keep up with the 450's, but not blow by then. So it really just depends on what your expectations are. If you just want something for fun that will keep up, go with a 310 ported by Neil like you mentioned, I think. If you are wanting to beat them or be at the head of the pack, then you need no less than a 330 if not larger, and consider stroking it.