Need answer FAST Speedometer gear????????

Depends on which drive gear is on the tailshaft. Mid model year '89 switched from 7T drive gear to 8T drive gear. To know which drive gear is on the tailshaft, look at the color of the gear, or count the teeth, or get the service part number's prefix from the tag (E6.. = 7T, E9.. = 8T).

Driven Gear = Drive Gear x Rear Gear x Tire Revolutions Per Mile¹ / 1000

A 23T driven gear with a 7T drive gear is just about right on...

22.96 = 7 x 4.10 x 800 / 1000
23.39 = 7 x 4.10 x 815 / 1000

But a 23T driven gear with an 8T drive gear is going to be WAY off...

26.24 = 8 x 4.10 x 800 / 1000
26.73 = 8 x 4.10 x 815 / 1000


¹Factory tires are at 800-815 RPMs. Aftermarket tires (with the same factory specs) are not necessarily at the same RPMs. Check with the tire manufacturer.