Motorcycle Repair: front forks, paul brodie, upper tubes

Question
i want to replace my front fork slider assy, to all chrome. i have an 87 fxstc. how exactly do i measure the existing forks, so i can order the proper length? the new ones come in stock length 24. 5. i measure from the center of the axel, to just below the top nut. i get 30.5. does that mean my bike came new with 6 over?  thank you PAUL BRODIE I KNOW THESE ARE THE FORKS THAT CAME NEW WITH THE BIKE

Answer
Sorry I didnt get back to you sooner. Seems all experts was having trouble with their web site and I couldnt get on.
Let me make sure I am reading you correctly. You are wanting to replace the bottom section of the forks only? If that is correct then order the stock ones. The upper tubes are the ones that change the length of the forks.
Good luck and happy riding
Mike