I was able to find the angle of the cab with this great tool. Digital anlgle finder.
Then I cut calculated how high I want this thing to be and cut the uprights to the proper angle. Remember you are cutting from 90 degress. I wanted the uprights to be at 72 degrees so I made the cut at 18 degrees.
Here is the upright.
These are the 12x5x 1/4" base plate. Notice the holes in this stuff, again more scrap. These plates cover up the front stake pockets. So I will machine a hole in them so I do not loose the functionality of the stake pockets.