TCI Gear Selector
Another really good computing url is
Bowling and Grippo Speedo Gear Selector
Speedo Gear selection program
This tool will ask you how many seconds it took to cruise a mile (using milestone markers on highway), what MPH your speedo said you were doing, and the driven gear you currently have and will tell you the best driven gear to use to make it accurate.
Now this is the BEST place, it will give you the percentile +/- that the gear
selection gives you, this way you can find that configuration that gives you
0-1% inaccuracy instead of 3-5% inaccuracy...
GM Jim's PDF