Is that wood? I would suggest using aluminum. I will post pics later of what I am doing for mine, it may work for you as well. I was going to make it like the Tamiya F350 and Tundra. The make some body mounts and call it good. I am going for simple and strong.

Here is a simple straight ladder style frame.



If my ladder frame doesn't work, I thought about something like this. Just some food for thought.