I could be wrong about this, but I thought the older 216 fan blades were, in fact, 16-inches across. About the same time GM converted to the full-pressure 235 ('53-'54), the fan size increased to 18-inches across. There are many posts on this site regarding overheating with the smaller blade, so I would agree that finding a larger blade is probably what you want. I use a 19-inch blade on my 235 that I drilled to fit my water pump (not sure what engine it came from). I have no problems with overheating even in very hot weather.
