If you want to run the staggered wheel widths like the V8 Camaro then you will want to reference the correct offset for those wheels:
6th Gen tire and wheel specs:
- 245/40ZR20 8.5Jx20 ET +25mm front
- 275/35ZR20 9.5Jx20 ET +39mm rear
5th Gen tire and wheel specs:
- 245/45ZR20 8Jx20 ET +35
- 275/40ZR20 9Jx20 ET +40
The seller may be correct that these wheels won't fit your Camaro. The offsets for the 5th Gen Camaro wheels are different than the 6th Gen so you will want to confirm the correct offset before you purchase. There are several vendors that offer ZL1 wheel styles so you won't have any problem finding wheels with the correct offset if the ebay wheels you're looking at aren't correct.
https://www.tirerack.com/tires/tiret...sp?techid=101&