First, they need to prove guilt beyond a reasonable doubt. Unfortunately in traffic court you are guily until proven innocent, but the burden of proof is still there.
If you know for a fact that your speedodometer said 60MPH, not 67MPH or whatever, then your speedodometer is wrong. Take the car and get the speedodometer calibrated. I know in my area we have emissions tests and they are done under pressure, so nearly every gas station that does emissions also does speedodometer calibrations.
The calibration will cost you anywhere from $20- $50 bucks. Find someplace that will do it, and if you have access to, or feel really sneaky you can swap the rims/tires for smaller ones, and throw more of a curve in the test.
With the calibration, you shed reasonable doubt that you actually knew you were going that fast. The lower your speedodometer says at 67 (since thats what is on the ticket) the lower you can argue in court that you did not know you were going that fast.
Whatever you do, go to court. Dont be afraid of going, and try not to be scared when you are there. Plead not guilty to both charges. Show your license and explain why you did not have it. If you get the speedodometer calibrated, show that and explain you thought you were going slower.
Try to talk to the officer before court begins. Ask him what he plans to do. They are very willing to talk with you and work out plea’s. I dont imagine the commonwealth, or district attorney will argue the case, but they might. The officer will tell you if thats the case.