Just go to ebay and order one there for a silverado. $151.00 shipped for the side rails and it comes with a templet to know where to drill. What year is your truck?
Sorry been to damn hot to go out and measure. I did cut 9" off the front and back of the side rails, put it together and just centered it on the roof until I liked where it was. Screw size was factory screws from 00-06 tahoe, and I used rubber well nuts to put in the hole on the roof to attach...
I am looking at putting a roof rack on my truck like a yakima or thule. Anybody got any pics saved where they might have seen one. Not sure how I would mount the rear one one since I have 3 doors. Detailed pics would be great but I'll take whatever I can get.