Hello Metalbender. If you would please tell me if you are using stock tires and rims? Is the transmission stock? Have you checked the speedometer pinion gear to see if it matches up with your rear axle ratio? Now if everything you checked out appears to be correct, the answer would be Yes. There are numerous establishments that can calibrate your speedometer for a fee. Here is what I found with a quick Google search: https://www.google.com/search?safe=active&rlz=1C1GCEA_enUS798US798&q=speedometer+calibration&npsic=0&rflfq=1&rlha=0&rllag=31985984,-100543601,1731360&tbm=lcl&ved=2ahUKEwjrpc7X_qffAhUQHzQIHUJAAZkQtgN6BAgAEAQ&tbs=lrf:!2m1!1e2!2m1!1e3!3sIAE,lf:1,lf_ui:2&rldoc=1#rlfi=hd:;si:;mv:!1m2!1d39.6283878!2d-74.8596539!2m2!1d27.231915299999997!2d-124.1865694;tbs:lrf:!2m1!1e2!2m1!1e3!3sIAE,lf:1,lf_ui:2

Sources: Google (Speedometer calibrations)

Every one I know is going to the GPS aftermarket speedometer If not available just use a Garmin GPS