I changed over a ROW hardtop to the convertible. I had an interior hoop, non-NAS, and it was a tight fit. Aside from having to make holes for the forward section of the cage you might have to add the side rope connections as well as something on the rear to catch the end of the rope. If you can get somebody to measure the rear ROW conv. top hoop to see if the NAS rear cage is higher? I no longer have mine. Most of the early ROW tops have a good amount of play so it might work?
Land Rover 110