When I replaced my radiator, I had to by new line joiners between new radiator and old lines as the new radiator had different threads.

 

Did not have that problem with wring threads. Still waiting on my new lines to come in but have another question. Is it transmission fluid that goes through all these lines including the ones to the external cooler?
Thanks,
Paul

1998 Disco I
1999 Disco II

 

"Is it transmission fluid that goes through all these lines including the ones to the external cooler?"
YES, it's one big closed loop.
If all you are doing is replacing the lines and fluid(At filter is more involved see link), then drain the fluild, replace lines, and refill.

This link will help, have a look> https://landroverforums.com/forum/di...-filter-34270/
Pic 2: drain plug removed. Pic 3: Look on the LEFT side and you will see the 2 lines that mount to the trans. 1 line is above the shift linkage and the other is in front of the AT pan(pic 4 gives a better view).
Now go wait for the UPS truck.