At least it has reasonable parts availability. Because it's a "Detroit diesel", it's post-1965. Before 1965, they were marked "GM Diesel" - because in 1965, General Motors reorganised and re-named their diesel engine manufacturing business from "GM Diesel Division" to "Detroit Diesel Engine Division".
In 1967, GM celebrated the one-millionth GM Diesel/Detroit Diesel engine produced. The first one appeared for sale to buyers in early 1938.
In my collection of brochures I have a superb 1938 glossy sales brochure for the "new" GM Diesel.
You would've been King of the Road or the Construction site with GM Diesel power in 1938 - but strangely enough, the 1938 GM Diesel sales brochure makes no mention of fitment of the new diesel engines to trucks or construction equipment.
The brochure aims the new engine specifically to buyers as a fixed power unit - for generators, ice and refrigeration plants, and industrial uses such as driving irrigation pumps, crushers and other major on-site power needs.
I don't know when the first truck appeared with GM Diesel power as standard or an option? I don't think it was until after WW2?
I do know that Allis-Chalmers rapidly seized on the GM Diesel as a power plant for their tractors not long after it was introduced. A-C had been having trouble trying to sell its A-C "Oil engine", which used a combination of spark and diesel injection - however it wasn't a true diesel and it was relatively low compression.
In late 1938, A-C built 10 prototype "LD" model tractors fitted with GM Diesels and tested them extensively for nearly 12 months. The results were conclusive, the GM Diesel was a winner.
In late 1939, the "LD" prototype tractor moved into full production as the "new" HD14 A-C tractor.
The U.S. Military was the biggest buyer of GM Diesels during WW2, and the majority of those diesels went into landing craft, and a modest number of military tanks.
Interestingly, Australia ordered the largest percentage of its WW2 tanks with GM Diesel power, as the diesel was much more fuel efficient, and had a much longer fuel tank range, than the tanks fitted with an aircraft radial engine.
Australian WW2 military chiefs were greatly concerned about the long distances the tanks might have to travel in Australia during wartime, with limited fuel supplies along those routes.
