Early PG cars used hydraulic lifters so the cams (and lifters naturally) are different. and they still made 216 splash oilers so that accounts for the journal differences. It was about 50-52' or thereabouts. It was a transition period for Chevrolet. So the engine application is important to finding the correct parts. There are many who can explain it better and in more detail if you want. Also you can find the info in the search area with patience.
Oh...and WELCOME aboard.
