Speedometer correction

It's time for some new tires and I'm thinking of stepping up slightly from the 245's that are on my truck, maybe a set of 265/75 or even go for the pizza cutters for driving in the snow out here and get a set of 235/85R16's Either way that I decide to go my speedometer will be off a bit and I was wondering what I could do about correcting the speedometer after I get my tires on.

George

I forgot to say, I have the automatic transmission.

I'll look later and get you the name of a neat little box I have on my truck (which I can't for the life of me remember right now) that splices into the wiring harness, you can adapt the speedo to read correct with the "pizza cutters" to 44" bog cutters

Superlift TruSpeed

Any downloader will also have this available.

Okay, had a brain wave come through and remembered LOL

http://www.abbott-tach.com/era.htm

That's the same one I have on my truck and with a little playing on the drive down with a GPS I now have a speedo that is about .3mph fast Over the course of a 218 mile leg of the journey down here to Titusville the odometer and the GPS disagreed by just under 1 mile. Kinda pricey at $145, but still cheaper than most good speeding tickets.

Where is the cheapest place to get a tru-speed?