For a V70 2004 offset is 49mm.
How much can I go less or more in a new wheel?

 

+/- 5mm should be no problem, -10mm should be ok anything more should be check ed with a pro. Note that if the rim width changes (ex going from 7" to 7.5) it can either make up for or augment the effect.

example, you choose a wheel with 40mm offset which in effect pushes your wheel outwards by 9mm. But you go from 7" to 8" width wheels which means that inside of wheel will sit 12.6mm further in. The net effect in that case would mean that wheel sits 3.6mm closer to inside (12.6 - 9mm) and comes out 9mm + 12.6 = 21.6mm.