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If you are thinking of an axle ratio change, than there is no need to recalibrate the speedometer because its signal is taken off the axle speed regardless of what differential gears you have.
If you are compensating for a taller tire diameter, than that gets more complicated. I think there may be aftermarket chips that can intercept the VSS signal and step it up or down to calibrate the speedometer signal, but thats beyond my knowledge.
92+ year trucks with the digital odo can be changed right at the dash board. Somewhere buried deep in my bookmarks is a thread, I think from this forum that tells you how to do it.