Hey XSesive, I just ordered and wired one in. Was super easy.
I ordered version# : 75-200 (silver) which is the version for "97-04 YZ's"
Mine came with speedo magnet cable, tach wire, and engine temp sensor (which I did not use). You will probably need to fabricate a bracket for where the speedo cable magnet pickup attaches below your caliper, I can take a photo of mine this weekend. A magnetic bolt replaces one of your bolts holding on the rotor that passes by within a 1/2" of your pickup to get speed. Set your wheel size on the unit and good to go. It comes with new bolt with a magnet to replace one in your rotors but it likely too small as it is for a modern YZ. I actually already had a rotor bolt with a magnet in the head from a previous electrnoic speedo I had. You'll probably need to pull out a rotor bolt and dimple it with a drill on the head to slip in the magnet flush.
Tach is easy, it has instructions but is basically a pos/neg cable - ground the neg, and the red wire splices into a wire off your coil.
At first my RPMs were a bit erratic but I think turned out to be a bad fuse.. replaced and it has been really smooth ever since. I'm going to consider what Grizld1 said and may splice in a 2 megohm resistor on the tach signal line close to the vapor.
It comes with a simple bar mount, or you can easily fabricate your own bracket out of some aluminum or something that mounts it a bit lower / flush.
So far I really enjoy it - it can be powered by its internal battery or wire it up to your bike's battery/main power for maximum LCD brightness (recommended). I enjoy the RPM visual display, and it also has an option/mode to show the actual exact RPM rather than the visual.. I was very happy when I switched to that mode as saw my bike hold a very stead 1180-1220 RPM idle.
The dashboard accessory is also very neat, and is basically just some LED bulbs with wires and plastic lenses.. you wire them up however your accessory needs. My only complaint was that the LED bulb wires led to a plug - from 8 wires to 6 - they double up on the negative wire for each pair of the bulb on either side (4 bulbs total). This means that if a switch uses the negative (like a neutral light) it can't be using the same ground as the highbeam indicator light (which uses the positive to make the switch). A bit confusing, but I found my own solution with some combinations.
