The 987/997 type knob itself would fit onto your shifter shaft, but the boot trim would not since it is a different shape. Therefore, you would have to modify it by mating the 987/997 type knob with a 986/996 type boot trim. This is what I did, and fitted a 987 knob to a 986 boot to put in my car:
Alternatively, you can buy them like this from a European retailer who does this for you at
www.carnewal.com. Just click on their 996 section and interior page, and then you'll see all the different shifter knobs they offer. Or, you can even buy their 986 boot with the silver horseshoe trim and mate it to the 997 knob. That will work too.