Yup, it's about 40% slow. I told the wife to just go by the KPH numbers, they line up within a couple percent now. So, how'd this come to pass, you say?
Well,..... In a fit of momentary ineptness, I managed to plug the tachometer wire into the speedometer! Whoopsie! Cranked it over, and sure enough the speedometer needle smacked the peg instantly. (only time that'll ever happen...:-) Needless to say, next time I see that wire, it's getting doubled over and taped away nice and fool(that's me)proof, as there is no tach.
Anyways! It's time to repair this thing, mostly because the odometer quit counting as well. Not sure if that's related, could be the usual gear, but might as well get it all functional and counting properly again. So, I've got two options: Either pester the local instrument repair shop into fiddling with whatever I managed to zorch, or: dig up a used one.
So here's my question: Being the electronic speedo, will I have to dig up one from a Volvo with the same gearing, (I'm guessing Probably!) and: If so, am I stuck climbing under my car and the potential donor with a grease pen and spinning the driveshaft to count the ratio, or is there a lazy man's way to avoid this?

There's a code on the speedo face that looks like "K9800" or
"K10080." Get a speedo with the same code and you'll be fine.


-b.

On the speedo face, even! It doesn't get much easier than that. Thank you very much, that's exactly what I was looking for!