I have a 1996 855 GLT N/A and I recently replaced the shocks and struts, it does not have the self-leveling suspension. For certain it is NOT true that all wagons have self-levellers. Most will not. It only came on certain models, maybe the R and with the heavy duty suspension package.

It is true that the self-leveling Nivomat is made by Boge, though Boge also makes the OEM standard stock. I know it is unlikely but can you see part numbers? If so look at http://fcpgroton.com/volvo850shocks.htm that may help you. And at http://www.rprusa.com/nivomat.htm there is a good description of the visual difference between Nivomats and normal.

Even if you have Nivomats, you can swap in normal shocks for the replacement but you'll have to get normal springs ($80/pair) to go with them or the rear end will sag due to the light duty Nivomat spring. Still, new shocks+springs would be much cheaper than replacing Nivomats. Replace the shock mounts too, they tend to break after 100k miles.
--
96 850 wagon