Now I can answer to my own question: Yes, you can.
You just have to:
1. buy a Pantera manufactured in 1976 or later, then you don´t have to mess with changing the floor pans.
2. get new seats which are as low as possible, and go as far back as possible. And you bolt them directly to the floor.
3. change the steering wheel into deeper
model (for example OMP corsica), it comes closer to you and your feet get more space.
4. forget the track driving, because there still isn´t enough space for a helmet. Or maybe you could use a plain plastic karting seat on a track?