Stovebolt engines are pretty simple, but there are plenty of places to make fatal mistakes if you don't pay attention to detail. If you've got a pre-1954 engine, the connecting rods do not have removable bearings- - - -the soft Babbit metal is bonded right into the rod and has to be fitted and clearanced by scraping the bearing to the exact size and shape of the crankshaft journal, then it's shimmed to the proper oil clearance. That's a skill set that has just about died out. Old geezers like me were about the last generation of mechanics to grow up around Babbit-rod engines.
54-62 engines are more powerful, and they have replaceable rod bearings. Lots of people retro-fit the older rigs with the later model engines. A little adapting is required, but not a lot. Unless you're planning to build a showroom-perfect restoration, the later model engine might be a better choice.
Jerry
