With an eye on the potentially lucrative US market, Marcos contrived a longer-wheelbase Mantis with 2+2 seating in a closed coupe style and the Triumph 2498cc six-cylinder engine. Initially this engine was launched in European TR6 tune, complete with Lucas fuel injection, but fitting the "federalized" version of this power unit for North American sale would have made sense. An overdrive gearbox is standard, with Borg Warner automatic transmission promised for the future.
The car's basis is a square-section steel tube chassis frame, clothed in the GRP coupe body, and though the details are different the front and rear suspension designs are like those of the smaller two-seater Marcos models, the front end being from the Triumph Vitesse, the rear axle from the Ford Capri 3-litre.
Marcos established dealerships in the USA but cars didn't sell and it was effectively total loss financially.
The company moved to new premises in Westbury, Wiltshire.