How many screws/bolts hold the valve cover to the head?

2 nuts on the top of the valve cover = 1953 or earlier 216/235.

4 screws/bolts on the edge of the valve cover = 1954-62 235/261

A 230, 250, and 292 would have (I think) more than 4 screws holding the valve cover to the head.

There are other distinguishing characteristics but the above information will get you closer.

The block casting number is at the upper right of the starter. The engine ID (serial number) is pressed into the block just to the rear of where the distributor enters the block.