Step side bed dimensions

[forestb]

My truck is at the paint shop and while it’s gone I want to build a peaqued roof for the bed of my truck to go under the cover so that it doesn’t turn into a swimming pool again. What I need is the length of the top from outer edge to outer edge. For the width I need the outside edge of the bed top rail to outside edge. I also need the inside edge of the bed top rail to the inside edge. If this is confusing I will draw a diagram of what I am looking for.