I have found a little book which I purchased years ago- "The Quad Field Artillery Tractor and 25 Pounder Gun by Cpt. P.R. Ventham R.A.". This booklet appears to be published semi-privately with proceeds from it's sale going to The Royal Artillery Charitable Fund. I have had a look on Amazon and it is currently listed as being un-available. Looking through it, I think that it explains the slight confusion above about engines etc due to the fact that there were 5 manufacturers of the Quad Artillery Tractor , 3 in the U.K. and 2 in Canada. The U.K. built Quads were made by Guy Motors of Wolverhampton with a 4 cyl 3686cc 53.1bhp Meadows engine, Morris Commercial with a Morris 4 cyl EH side valve 3519cc 70 bhp engine and the Commer-Karrier with a 6 cyl Rootes group 4085cc 80 bhp engine. It doesn't state which Rootes Group company produced the engine but it does suggest that it produced 400 of the Quads exclusively for the Indian Army. The Canadian produced Quads were made by Ford and G.M.C. (Chevrolet). The Ford Quad had the Ford V8 3916cc 95 bhp engine as you might expect and the G.M.C. Chevrolet had the Standard G.M.C. 6 cyl 3548cc 85 bhp engine. The 2 Canadian made Quads were very similar vehicles, apart from the engines, with many interchangeable parts.
Does any-one know if the Morris Commercial Quad and 25 pnd Field Gun set that use to be on the U.K. show circuit about 25 years ago is still about or has it gone abroad???