I adjusted my Roadster rack way back because it was adjusted too loose. It's fiddly to do on the car, and you need a big open ender, but I managed it.

Found it! Scroll down for the images:

http://www.talkmorgan.com/ubbthreads.php/topics/44835/Classic_Traditional_Cars_Steer#Post44835

In the MGB workshop manual, the factory used a special tool which comprised two cones fitted on the end of each part of the steering column to achieve perfect alignment.

DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4