Hi George,
Yes the channels under the box are odd. I believe the box was welded together with another to make a grain carrier. You can see where it was welded together. Someone actually added another piece of channel iron on the original channel forming a box like tube. That is the difference. It certainly reinforced the channel. I will keep this way and put a strip of rubber along between the frame and the channel. I have been busy cutting out rusted out areas of the box.
I had a new front window delivered for my house. It was put in my shelter beside my truck. Not thinking about it except to make sure I don't drive into it...I started cutting and grinding away on the box. The weather was good so I decided to move the truck onto the driveway to work in the sunshine. I walked back into the shelter and looked at the window....oh NO!!!! the grinding I was doing was hitting the glass....the window is now pitted from the hot grindings....DAMN!!!!!

oh well...good thing the wife is on vacation...I should be able to get the glass replaced before she gets home...

I will have to dip into my Slush fund .....

Chalk up another one for "lessons learned".
George, If you can fix me up with a pic of the rear panel where it attaches to the angle iron that would be great....both at the top and the bottom.
cheers for now....
Mike Timoshyk, feeling the "pits"