If you can show a few photos of what you have and can see at the moment. That will help a lot. The cable itself will be tied into a bundle of other cables, wire and more that you don’t see under the floor boards.
It‘s a job that has been done and able to be done by others here. You just need to follow the cable and measure as you go along and allow for the gradual bends you find.
I did mine on my 340. The cable bundle ties were the type that were screwed into the side of the stringers and I was able to unscrew them and allow slack so the new cable could be fed through.
I wasn’t lucky enough to be able to tie the new cable to the old and pull it through. But all in all it wasn’t the hardest of jobs. Contact the store here on this site, they may have the proper length requirements you need.
I have photos in my media here that you can take a look at also.