There was no 1954 216 engine. Maybe you are referring to a 1954 261 water pump?

Nonetheless, I think the 1954/55 235/261 water pumps were similar to the older 216 water pumps.

I am also interested in seeing what people say about the fan shroud diameter in a set-up as you describe. I'll be doing what you describe on a 1960 261 with the water pump adapter plate and an older style water pump with the 53-55 3/8" pulley, and a 1954 3/8" harmonic balancer. I'll probably use the 3/8" pulley and fan off a 1954 water pump.

Tim