Find the number that's stamped (not cast) on the machined pad just to the rear of the distributor and post that for us. Most likely a 1950 big truck would have left the factory with a spray-oiler 235 engine, but there's no telling what might have been installed since then. If it's got a sheet metal side cover on the passenger's side that extends up over the cylinder head and the spark plugs and 2 bolts in the center of the valve cover, it's either a 216 or an early 235. A short side cover and 4 bolts at the edges of the valve cover would probably make it a later model 235. The block casting number down near the fuel pump and the stamping I mentioned before will ID it accurately.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!