Taking a sport ARF to those speeds might be reckless and/or dangerous. If you plane to do this, reinforce as necessary and lighten along the way. You will need to put all of your controls internal to the plane and clean up the airframe in general. Then add a high torque engine with a huge pitch.

Your better solution would be to buy a purpose built racing plane. There are plenty of racing P51's out there. Post this question on the racing forum for working examples.

Mark M.