Parcel shelf will require doubler plates as a minimum to have enough strength for a harness. The baby seat mounts are not designed for a harness.
Options are:
Meridian Motorsport Harness Bar which sits above your parcel shelf:
Custom Race Fabrication, Roll Cages, Harness Bars, Seat Mounting etc.
Put the eylets inbetween the seat cushions. This is pretty close to iffy as the angle of the harness is not ideal, but still legal.
Just pull the seats out, only takes a few minutes to do.
Then you can get into the debate of how safe it is to run a harness without roll over protection. A lot of people won't run with a harness unless there is a roll over bar, half cage, full cage etc due to the way the roof crumples and the lack of movement in a harness.