[OldGMJon]

All good advice thanks for responding...Sacramento is about a four hour drive from here though.

Originally Posted by jtrichard

IF you like the mileage/power and look of the tire size you are running you can use one of these it will bring your speedo real close http://www.ebay.com/itm/AC-Delco-Ste...b671b5&vxp=mtr

Originally Posted by bhc41051

I think you might be putting the cart before the horse on this one; why don't you call a speedometer shop. I have no experience with this place. But they're kinda sorta close to you. https://plus.google.com/103811379957...04/about?hl=en

Originally Posted by markeb01

I'm not sure changing tire diameters is the best approach to speedo accuracy this many years after production. Too many thing may have been changed over the life of the truck. The ratio adapter noted above may help, but it might not be the ratio change you need.

A speedometer shop would be the best bet as they can simply change the plastic driven gear in your transmission to one that gets you very close to a correct reading: