Cross Rails for a short bed fleetside.

[rmvlt1100]

I was wondering how many cross rails are needed for a 1965 C-10 short bed fleetside. When I bought the truck the bed was apart I only got 3 cross rails with it. I have never put together one of these beds before and not sure how many rails that I need. I have seen anywhere for 3 to 5. If anyone has pictures of the different steps of putting a bed together that would be great to. My bed should be back soon from the body shop and want to put it together and see what other parts I need for it. Thanks n advance.