With the apparent technical advantages of this concept laid out, Max Mosely (Herd's partner at March Cars) pressed for a prototype to be built. Max was more business-minded than Robin and had already noted that the P34 had been a tremendous publicity coup for Tyrell. Aside from the technical merits, he believed a March six-wheeler would be an irresistible package to present to potential sponsors.

The car was designated as the March 2-4-0 following the practice used to describe railway rolling stock: Two wheel steering, Four wheel drive, Zero differential.

Unfortunately, the March team was at something of a low point financially during 1976/77 and developing an all-new six-wheel car would have been too expensive. As a compromise measure, a 1976-design Cosworth DFV-powered March 761 was adapted by team engineer Wayne Eckersley in a quiet corner of the Bicester factory. Existing parts from the factory stores were used wherever possible.

But this wasn't the only compromise. A key feature of a car with four driven wheels at the rear would be an ingeniously-designed and very strong gearbox. Ingenuiety was required to minimise any frictional power losses. Increased strength would be needed to counteract the higher torsional and flexural stresses that the close-coupled four-wheel-drive system would generate.

Herd's original design for the gearbox casing recognised this and specified a series of heavy strengthening ribs to counteract the additional loading. But at some point in development, after costing the design, it was decided that the casting would be too complex and expensive to produce as it was. By way of a cost-cutting measure, some of the ribs were duly removed from the drawing.

In fact, the design used a standard Hewland gearbox for the first axle. To this, the new casing, gears and an extended pinion for the second axle were fitted. Practically, this meant that any 761 chassis could be easily adapted should the concept prove workable.

Once the 2-4-0 was partially built, the press were invited to the factory in early December 1976 for a viewing of the hitherto "secret" project. In truth, the striking flat-white chassis Herd presented to the press was little more than a full-scale mock-up but it generated a huge amount of excitement - making the cover of that week's Autosport. On top of this, the assembled journalists were promised a full running demonstration at Silverstone scheduled for a fortnight later.

All hands at Murdoch Road were now duly pressed into service and a proper running car was made ready on time. Unfortunately, the inevitable happened. Within half a lap the gearbox casing flexed and the gears became unmeshed. There was no time to make a new stronger casting and so the rear crown wheel and pinion were quietly removed. Effectively it had become a two-wheel drive car again. Fortunately for March, it was a wet day at the circuit and the driver (Howden Ganley) could not push the car too fast and the test was deemed a success by the assembled media.

Whatever the press wrote, there was no escaping the fact that the car needed the new gearbox casing and a serious development program. Unable to afford the time and resources that this would require, the 2-4-0 project was put on the "back-burner".

The car was eventually fitted with a stronger gearbox and ran at Silverstone in February 1977 with Ian Schekter at the wheel. Although it was another wet day, the car was run up and down the Hangar Straight and, with four driven wheels, Scheckter reported that the traction was incredible. More importantly from Mosely's perspective, the car - in it's new blue & white Rothmans livery (March's main sponsor at the time) - again made Autosport magazine's front page. The car also appeared briefly in practice at the 1977 Brazilian GP although it did not race. But this was the end of 2-4-0's Grand Prix racing history. When it reappeared at the Belgium GP in June, the 761 chassis had been re-converted back to four wheels.