The Coupé is a mid-engined two-seater sports car designed to give outstanding performance for its time, and impeccable handling. The design composed of two Mini front subframes, with traditional Mini rubber cone suspension, linked by a sheet steel semi-monocoque chassis. The chassis' deep centre tunnel backbone is supplemented by two generous sills. The car is mid-engined: the rear subframe contained the engine as in a Mini with the steering arms locked in position with adjustable rods and ball joints. This is held in place by a 1" square tubular space frame, all the way from the rear bulkhead. The front subframe carried the steering rack, fuel tank and radiator. Brakes and wheels remained as per the options available to the Mini, post April 1982 GTM coupes being designed to allow fitment of 13" wheel.
The chassis is fabricated from 18-20 swg steel, to incorporate the floor pan, boxed sills and the central tunnel box section. It forms a very robust structure. The fabrication is carried forwards in order to locate the front sub-frame, and a 1" square tubular space frame extends beyond the rear bulkhead to carry the rear sub-frame. Welding was carried out by MIG for consistent quality and to avoid distortion. The chassis was fully jigged during manufacturing to ensure a true and accurate assembly.
The body is moulded in high quality glass reinforced plastic. It is extremely tough, non rusting and, being unstressed, is not subject to gel-coat star crazing as found on many cars using GRP body shells. The windscreen is laminated glass and the rear screen perspex.
The doors are double skinned glass fibre fitted with anti-burst locks, steel window frames, and steel strengthers to avoid door drop, often found on glass fibre cars. The sliding windows are toughened glass, coming from the Mini traveler.
The bonnet is again moulded in high quality glass reinforced plastic. It is hinged at the front to give access to under bonnet space.
Completely separate boot compartment situated behind the engine, offers 4 cu ft (0.11 m3). of luggage space with separate locking boot cover. The car was available in several groups of "part packs" that were designed to allow each stage of the build to be purchased separately as they were undertaken, spreading the costs over a period. In 1985 a complete kit cost £2380.
"Labour packs" were also available for customers that wished GTM to undertake specific stages in the construction.