A 4 point harness is tough to use with stock interior. There's really nothing to bolt the shoulder harnesses to. My Camaro has a rollbar, as does my gasser, so both use harnesses. The gasser uses Harwood racing buckets that have a place to run the lap and shoulder belts through, so a bar could be installed behind the seat to attach them to. But stock vehicles and stock buckets wont work even if a bar was added, as there's nothing to stop the shoulder harnesses from slipping off your shoulders.
If you do add a bar for a harness it needs to be shoulder height or higher, as below shoulder height will cause a safety issue. In a crash the harness would pull down on your shoulders and cause bodily injury if the point of attachment is not at or above shoulder height. Problem is a bar this height will limit access to the backseat, so you need to decide if you really care if anyone can use the backseat, or if your car will become a 2 seater with shoulder harnesses.
Last edited by 1971BB427; 01-17-2012 at 07:29 PM.