How can you disable the speed govenor on a used GMC Penske truck that you purchased?

On or near the floor, between the drivers seat and drivers side door, there will be a protruding electrical inlet (usually grey in colour). A mechanic has the means to plug a contol box into that inlet, and can alter the settings of the speed governor, which includes leaving it wide open. The process itself should only take about ten minutes or less, but you will need to go to a GMC dealership to have this done, unless you can find a third party mechanic who has a compatible control box.