M20 Speedo cable length

[Mark Barkntrunk]

Hi I have a broken inner speedo cable for my 1942 M20. The external cable is 25" I need to know the internal length of cable please. I brought one that measures 26 5/8". Would this work. Unfortunately i'm Not able to put it on the bike to see as I've been unwell. Hopefully someone will know the correct length or where I can find it?
Thanks
Mark