From what I can remember about harness and fitting locations, if you have the shoulder straps coming out of the seats and heading straight down, when you have an accident the forces are transferred downwards and through the seat which usually ends up in the seat splitting at the point where the seat bottom and back rest join.
Schroth harnesse have a quick fit system that uses the original inertia reel points in the front and back and has a quick connect system that allows you to take them out in minutes.
Have a look here Rallye BeltQuick Fit
Or they do inertia reel ones that require a higher fitting point but would still alllow you to look forward at junctions/ change the Britney Spears cd that the mrs left in there.
Cheers
Martin