I should point out that the pump in the article is a Buick pump and not a Rover pump, although the footprint of each is the same. The P6B water pumps have the shortest nose of any water pump fitted to the Buick / Rover V8. The only variation is in the fan and its attachement. The depth of the steel fan once fitted to the pump is somewhat greater than the 13 bladed nylon fan running on a viscous coupling. The latter is far more efficient, both moving a greater volume of air per revolution along with being speed limited to 2500rpm thus reducing the engine's fuel consumption at revs exceeding that figure.
The nylon fan with viscous coupling came fitted as standard on all CKD New Zealand assembled Rover 3500 sold in Australia. The U.S NADA cars and I am guessing here those sold to Middle Eastern destinations may well have had them as well. Although the U.S might not necessarily be classified as a hot country, both Australia and Saudi Arabia etc are.
Ron.