How do i calculate what speedometer gear i need ?

[X MONTE SS]

I recently bought an 85 k5 with a turbo 700 and gear change from 3.08 to 4.10. My speedometer is way off and i want to recalibrate . Anyone know what speedo gear i need?

 

[txbluethunder]

what tire size?

 

[txbluethunder]

http://coloradok5.com/forums/showflat.php?Cat=&Board=blazer4x4&Number=516195&Forum=blazer4x4&Words=txbluethunder&Match=Username&Searchpage=0&Limit=25&Old=1year&Main=516188&Search=true#Post516195