Had a similar issue when replacing the water pump on my 3.9 Plus 8.
Never realised so many different versions were fitted to the Rover V8.
Eventually identified the correct short nose pump as the same as fitted to the Triumph TR8 installation.
Bought one at a very sensible price from a TR8 specialist in Hertfordshire.
Getting the two long bolts, that penetrate the water jacket, out was A MISSION!
Have kept the original for... what? Just a born hoarder, I'm afraid.
