reprogram speedometer for gear change?

I'm changing from 308 to 373. how do I reprogram speedometer to show correct speed?

this seems to be dependent on what tuning software you're using and what transmission you have, along with the year.

I have no knowledge of what to do or how to do it. I need someone to direct me where to get the info on how and what I need

there is a good chance that someone here will help you and walk you through it, but you wil have to give info on your car.

y or f body, year, wheel size and the transmission. Also needed is what tuning software you are using. No one can help you do anything without this info.

The bare minimum is that you will have to send the computer out with the info I just mentioned to a mail order tune place, or pay a couple bills for a box to change it.

I'd help you personally but I'm trying to find out the same info.

I have no knowledge of what to do or how to do it. I need someone to direct me where to get the info on how and what I need
If you can't provide the simple car info that nov194 asked, there isn't anyone that can help you.