Another very interesting and informative M-H thread developing here.
In respect of your first post Joe and the GP pictured at our Carrington Rally in 2011 with one of Robert Crawford's service vans in the picture, this tractor is not one from his collection, it is owned by a collector in Norfolk, I can confirm it is an owner creation, everything forward of the bell housing was missing and he put in the six cylinder engine, together with making up the radiator and bands between the spade lugs on the wheels, they are not original M-H equipment, but expect they work well and act as a directional skid ring in the field as well as a road band to keep the lugs off a road surface. The owner at the time of this retoration had a large contracting business and found his stone crushing machines used "twin disc" slip clutches from the USA, he contacted the company and they sent him a clutch to fit this GP, I was amazed to hear Twin Disc are still in business manufacturing clutches.
Malcolm.