When they say "larger trucks" they mean 2 ton and larger. The 1/2 - 1 1/2 tons had the 265. That was also the base V-8 in the sedan delivery. The main reason that the 283 was even available in the s/d was that it was a passenger car, and therefore was available with any passenger engine, even the 283 horse feullie engine.
Now that's not to say that if someone made a large enough order (at least 50 units) that the 283 would possibly been installed, it's just unlikely, as trucks are mainly utilitarian vehicles.
