We had a welder friend fabricate the roll hoop in our 71 coupe. We wanted it to stiffen the car a little, offer some protection and allow us to bolt up the 5-pt harnesses. We have just enough clearance to get the rear window out...not a 1/4" to spare.
With the seats back most people don't even realize we have the bar. There are more pictures of the fabrication on our website.