Go with the 10 ft.
I just replaced mine on H34 and it was 10ft.Carefull backing out the screw that crimps the cable into the coupler at the engine. Mine needed replacing since it was rusted and I broke the head off the screw. You will also need some new panel mount tie wraps since you will have to cut these to get to the cable out of the harness protective wrap. Otherwise a very easy job - around 1/2 - 1 hour total.