I put 3.73 in my 1996 camaro had 2.73 now it shuts off at 120mph on the speedometer but i am only running 85mph. how do I recalibrate the speedometer?

I think it would take a recal of the computer. I have an HPP3 programmer for my SS and one of the prompts is to recalibrate the speedo for a tire size or gear change.