The things that make that speedo jump are funny as hell. :laugh:
The speedo was acting up on our 00 SVT a couple weeks ago, which I believed to be a failing fuel pump. The needle would bounce around between 0-10 MPH while sitting at a dead stop. I noticed the voltage would dip a little around the same time, and the fuel pump made some strange noises. I would blip the throttle, voltage would regulate and the needle stopped moving. The fuel pump has been replaced and it hasn't done it since. I'm not saying it's your fuel pump at all, but strange things can happen to that speedo when the electrical is acting up.