The Desoto /Chrysler / Dodge Truck engine your referring to is 238 ci, 250ci and 265. They all weigh within 2 pounds of each other. They are all 3 7/16" bore and use different rods and cranks to get to 238 ci - 4 1/4" stroke, 250 - 4 1/2" stroke and 265 - 4 3/4" stroke. While the Desoto never had a 265 ci motor stateside, after Chrysler and Dodge Trucks have them in 1952, you could but the 265 in the 1953 model year in Canada, just like Plymouth could be bought with a 250 ci motor later. Yes I realize people often refer the 250 as a 251 or 252, but I am just going by what Chrysler called them.
In any case those engines are 422 pounds. That is the engine.. Not bell housing, not intake, exhaust and carbs, pulleys, starter etc, but does include the distributor. I haven't scaled one with all the accessories on it, but someone's estimate of 450 lbs is likely pretty darn close.
Our 265 engine in our race car, including the intake/exhaust, carbs, ready to hook up to the bell housing weights 410 pounds. There is actually a lot of weight you can take out of the engine if you really want to
Tim