I thought I'd pass along some information I found not too long ago about the Canadian 224 motor.
After much searching, I finally came across a little history on the elusive Canadian GMC 224 engine. I found this on a website describing the history of th BRANDENBURG OPEL TRUCK PLANT. Here is the paragraph:
"In 1936, and I assume here that the American deputy chief engineer at Opel Russell S. Begg was responsible, a new engine was designed for the forthcoming Opel Admiral model. The engine for this large Chevrolet-sized car was based on the new 1937-on 216 cu. in./3,549 c.c. 6-cylinder Chevrolet engine, with four main bearings. The Opel engine was copied from the Chevrolet by redrawing the original blueprint drawings and converting from Imperial to Metric measurements. In fact, at the end of the day the engine more closely corresponded with the Canadian Pontiac car engine for 1937, the 224 cu. in. unit, which was fitted into a Chevrolet-based bodyshell to create the Pontiac 224 model and also in Canadian GMC trucks. The “224” unit was created by increasing the Chevrolet 216.5 unit bore by 0.0625”, with aluminium pistons instead of cast iron. The Bore & Stroke were then 3.5625 x 3.75 in. [3 9/16 x 3 ¾ in.] [30.2 H.P. rated engine measured exactly at 224.1 cu in. The Opel engine became 90 x 95 m.m. Bore & Stroke, the nearest Metric equivalent, or 3.5433 x 3.74015 “, for 3,626 c.c. [Rated at 30.1 H.P., producing 86 b.h.p. @ 3,200 r.p.m.]. The Opel car engine had a 6:1 compression ratio as against the Chevrolet 6.25:1, and used the same transmission ratios as the Chevrolet: 2.94:1, 1.68:1 and 1.0:1. "
