There are two styles of pumps used on 235s originally.
1941-54 (not called a short pump but is) and
1955-62.
The 41-54 pump mounts on the face of the block and has two holes about 1 1/4" in diameter that transfers water into the engine. These pumps put the shaft at head gasket height.
55-62 pumps sit 3" lower and the impeller fits inside the large hole in the front of the block.
The 55-62 pump is much longer so if used in a 54 or earlier chev needs to be shortened. ie short shaft pump.
