be careful when mounting them...angles mean everything.
you don't need an anti-submarine belt unless you have an open wheels car where you basically lay inside the cockpit.
most harnesses are illegal for highway use unless there is a DOT approval.
be very, very careful when you choose your mounting points. always brace the bottom side if you don't use factory mounting anchors.
i've used both the manually tightening type and the type with the retractor. you'll probably lose use of your back seats in order to use the proper mounting anchor points.