You could always do what i did, which was to put a set of 3 pt. Double release belts from Corbeau.
They go through the holes in the top of the seat, then bolt into the existing holes in the back seat belt brackets. Just thread the belt between the upper and lower half of the back seat. If you want folks in the back, you just unbuckle the top half of the belt and you are good to go.
The only down side is that folks in the back wont have a seat belt. This is safe according to Corbeau, it was in their instruction manual that this is a safe way to route the blets. Otherwise i wouldnt tell you to do it LOL
Just please, please, please do not bolt the shoulder straps to the floor right behind the drivers seat, its is very very unsafe.
here's a pic of my install
