The odometer is easy to fix and you'll put in four (or six) new bulbs at the same time. It shouldn't be too expensive, most likely a lot less expensive than getting another cluster. If the 850 has ODBII (from the late 95 models), you could get it to work with a '97 or '98 S/V70 cluster. Found an arc...

Speedo gear goes bad, this is usually due to trip being reset while the car is in motion. You can either buy this https://www.ipdusa.com/products/4709/109979-850-odometer-gears-instrument-cluster-bulb-kit Or buy the speedo gear but get some LED for the dash like I did. https://www.ipdusa.com/product...