From the listing for this Group B Rally Car for sale:

This motor car offered for sale by DK Engineering is an international specification Group B MG 6R4 rally car. In period, Simon Taylor (of Haymarket Publishing) and David Power (of Power Engineering) shared it in hillclimb events at famous venues such as Shelsley Walsh, Prescott and Gurston being prepared by Power Engineering. Following a competition event at Prescott in May 1987, whilst at the hands of David Power, it was deemed necessary to replace the front wings, the front end of the car was then upgraded with a set of extremely sought after and rare inner front wings that were constructed in aluminum with honeycomb reinforcement. These evolution wings were bonded and bolted to the front bulkhead and chassis beams and had been made up prior to the Sanremo Rally of 1986 and fitted to the Pond and Wilson cars for that rally. It is believed they were later removed prior to the RAC Rally of 1986 and were consequently purchased by David Power from the works stores at Cowley. These parts are still fitted onto the car today. According to an advert published in Motorsport News in 1992 the car was built on an ex-works shell, but a recent inspection shows that this is probably restricted to just the front end modifications as described. From Wikipedia:

Created for the short lived Group B race category, the 4WD mid engined MG 6R4 (6-cylinder, rally car, four-wheel-drive) Metro of 1984 was a world away from the best selling supermini to which it bore only a superficial cosmetic resemblance. The competition car effectively only shared the name of the production Metro as it featured a mid-mounted engine with four wheel drive transmission enclosed within a seam-welded tubular chassis. The development of this vehicle had been entrusted to Williams Grand Prix Engineering.

The resulting car was shown to the world in May 1985. It was powered by a David Wood designed bespoke 3-litre V6 powerplant which used some of the engine architecture of the Cosworth DFV. It featured twin overhead camshafts and four valves per cylinder. The engine was a break from the norm, as it wasn’t turbocharged as the majority of its competitors were. The engine was mounted back to front in the car, with the forward end of the engine facing the hatchback and the gearbox attached conventionally behind it and, therefore, in the middle of the vehicle. The four-wheel-drive was permanently engaged, and drove separate propshafts to the front and rear differentials. The rear differential was mounted on the side of the engine sump with one driveshaft running through the sump to the nearside rear wheel. Much of the outer bodywork was made of GRP, with the only exception being the roof panels (which were aluminium) and the steel doors. These were, however, concealed by plastic airboxes. Indeed, models now on show generally have stickers demonstrating where it is safe to push from when moving the vehicle, so as not to damage the bodywork.

The 6R4 appeared in two guises. There was a so-called Clubman model which was the road going version which developed in the region of 250 bhp (186 kW), of which around 200 were made and sold to the public for £40,000 (the homologation version). A further 20 were taken and built to International specifications which had a recorded output of over 410 bhp (306 kW; 416 PS)