Unlike conventional bodyshells which are simply decorative, the GD body is a semi-monocoque design. Careful use of different fibreglass materials (such as woven rovings in the side sills) and techniques (such as Cormat sandwiching in the footwell areas) endow the GD427 with great strength and high levels of occupant protection. This is further enhanced with foam filled side sills and substantial anti-intrusion beams in the doors.

Because of this strength the bodyshell can be isolated from the chassis through comprehensive use of rubberised mounts which reduce vibration and noise in the cockpit. The monocoque design means there are no inner panels or floors to bond in place, making trimming easier and ensuring a watertight environment. Finally, the whole body can be removed from the completed car's chassis in around an hour for major servicing or repair work - yet another completely unique feature to the GD427.