Having read the method on line that didnt work we had to try something else
We tried DW 40 and Heat but that was not the answer either
Nissan can no longer supply the original part but an updated unit is available from NZ DATSUN PARTS
Replacement Part NO 21045-MO100 $50.00 plus Courier
This is a standard unit on Datsun Utes and Datsun 120Y
Firstly using a cold chisel cut a V into pipe close to motor casting
This breaks the rust away from the pipe and squashes it and then it can be pulled out with vise grips and tapping with a hammer
You also need to also pull it like removing a tooth action
New one can be tapped in with a block of wood and hammer
We applied loctite as it will be never be coming out again
The heater hose can now be reconnected to the new pipe elbow and the Tee Piece which is exsisting removed
A copper joiner can be made from a piece of 25mm pipe from your local friendly Plumber
Make sure to get your Plumber to roll / flare both ends to give better grip for the hoses
Rubber hose not the fabric type is better value I have found
Mine had lasted 49 years before it started leaking
Good luck