[Snake2998]

Three important rules:
1 If you have no roll bar and full harness don't roll it - rather have lap strap only. You don't want to be held with your upper torso and head acting as a roll bar in an accident - rather lose your teeth on the steering wheel or dashboard.
2 If you have a properly mounted traditional roll bar make sure there is no way your head can hit it in any accident.
3 Accept that the car is intrinsically unsafe for all occupant in an accident, and if you cannot accept that, sell it and buy a modern sports car.

The above is strictly my opinion and uninformed by research or special knowledge.