[Ok here we go]

First of all, noice seats!

Please correct me if I'm wrong, but my understanding is that one way to re-use the seatbelt receptacle for vehicles with powered seats is to use a new seat bracket that is compatible with your seat and that has a seat belt attachment point.

An example will be The Planted bracket:

https://www.plantedtechnology.com/planted-seat-bracket-porsche-911-928-944-968-964-993-1974-1998-driver-left.html

I believe the order goes: floor - bracket - rails - seat.