An interchangeable passenger seat for a vehicle having a seat-mounting surface includes a base frame having at least one end member attachable to the seat-mounting surface of the vehicle, and at least one cross-member extending generally perpendicularly from the end member. At least one back frame is removably attachable to the base frame. An adaptor bracket is disposed around the cross-member. The adaptor bracket has a plurality of locating structure along the length of the adaptor bracket for selectively locating and attaching components of passenger restraint systems.