I have some recommendations for you my chevy drivin lil buddy. What I would do 1st is box the rest of the frame... maybe bend 2 pieces of tube _/------ something like this and box them inside of the existing frame that will give you the rear frame rails with some room under for articulation. then gusset n box the 2 piece frame rails on each side and shape them as you need. here is an example from pirate that I saw.. looks like an awsome design
