CHEVROLET VAN INSTRUMENT CLUSTER GAUGES SPEEDOMETER

I've Replaced A 3:52 Rear End With A 4:11. What Do I Need To Do To Get The Speedometer To Read The Correct Mph? Van Has A 5.7 With At.

1997 Chevy Van 142000 Miles My Car Bucks On And Off. It Feels Like Its Revving And Then Slowing Down. The Speedometer Stays At...