I'm looking to pick up an extra set of wheels to run winter tires on. Are these the correct wheels for an 02' 996T? Not sure if I need any offsets for these. These wheels in particular are noted to come off a 2005 C4S and owner say they have spacers for the rear.

8Jx18 ET50, Porsche Part#: 996.362.136.51
11Jx18 ET63, Porsche Part# 996.362.142.52

Also, what might these wheels be worth? Buyer is asking $1700 and they look very nice in the photos.