Just be careful since the 981 was designed for 20" rims and corresponding profile tires, whereas the 987 was designed for 19" rims. The actual diameter of a rim + tire (wheel) on a 981 is 1" greater than on a 987. So you should check to be sure the total wheel diameter is suitable. I would also suggest checking the offset just in case there is a difference, but I imagine it is minor, if at all.
FYI, these are two pages from the Porsche Service Information booklet for my 2006 Cayman S (987). The wheel & tire size information may be of some use to you.