Since the engine isn't "original" to the truck, it would probably be wiser to find and rebuild a later model, different design engine. Chevy 235 engines from 1954 to 62 have a different lubricating system, and connecting rod bearings that can be replaced. Edit: I see that the rods have already been machined for insert bearings, but those bearings are almost impossible to find these days. If you do find them they are terribly expensive. 216 and early 235 engines have Babbit metal bearings made into the connecting rods. Your pictures show aluminum pistons, which were used from 1954 through 62 in 235 engines. The 1948 235 had cast iron pistons originally. Main bearings for 48-53 engines are also unobtanium! 54 and early 55 235s would be a bolt-in swap for your truck, and late 55 to 62 engines only need a modification to the water pump to fit properly. There is also a 1954-62 261 cubic inch engine that would fit with very little adapting. Rebuilding parts for the Babbit-rod engines are extremely scarce, and people with the skills needed to do a good rebuild on those engines are either geriatric, or on the brown side of the grass!
Jerry
