The wagon and sedan have different mount points. The sedan is further
forward and requires a wider front cross bar. The load bars actually
have an icon of a wagon on them for the wagon (and a sedan for the
sedan model, I supose).

My wife has an 855 and we purchased the factory load bars.
I am able to use them on my 98 S70. But, to do so I cut the front bar
and inserted a spacer then bolted it back together. The spacer has
two positions: wider for the sedan and narrower/original width
for the wagon.

The V70 body also changed a lot around 2000 and that model seems wider (in
case they are for a 2000+ V70 and not a 98 or 99 V70).

So, if you want an exact fit you will have to get them for the sedan.
If you are good with a hack saw and minor metal working (and have a
hardware store close by) you could probably make them work by cutting
the front bar in half and figuring out how to make it wider (it is a
bit of an ugly work-around in the Frankenstein mold, though).