Here's a picture to give you an idea what you're up against. You can see where the cables pass through from the cabin (red circle). The green lines show the clips that hold the cable housings in place. The red lines are showing the nuts which hold the actual cables in place. You've got to loosen the nuts and remove the clips on all of the cables in order to pull them back through from the cabin. And then you've got to be able to feed the new ones through and hook everything back up. You *might* be able to see all of the cable ends without pulling the tank, but trust me, you can't get a wrench on them with it in there.
This picture only shows one of the flapper boxes, there are two more you need to consider as well.
Good time to clean and seal your gas tank, clean the area under the tank (make sure to tell us what kind of tools and other goodies you find down there), possibly replace soft fuel lines with stainless ones, etc.
Good luck!
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