speedometer

I'm not 100% familiar with the exact parts you'll need for this, but I would probably look into various resistors. Get the reading from the speedo wire to find out what voltages are for what speeds you want to indicate with the LEDs.  I would then use the resistors that will prevent lighting up until a certain voltage is reached. That should give you a start. From here it is a matter of getting in touch with an electronics specialist/technician (preferably technician) to figure out what resistors you need (also dependent on your LEDs so I would start with the LEDs and work back from there)

Good Luck!