Isn't the worm gear for driving the speedo?
Oh! - should have read the question more carefully!
So yes - I'd change to a digital speedo, driven off a wheel.
Been on my 'to-do' list for years...
Then just glue the old worm gear in place to stop it moving, and causing any other issues, after removing the rest of the old speedo drive gubbins.
Gain more BHP too!https://www.merlinmotorsport.co.uk/p/racetech-80mm-electronic-speedometer-rtsc130