This is where, if you don't have access to a welder, then you need to invest in one.  We have a Hobart Handler 120 and it has been Great!  You will want to locate an inexpensive place to buy your steel.  You will need several pieces, probably over $500 - $800 worth or more, depending on how much you do.  The Stretch is needed for the body.  And all the other steel is to give the body more support in the appropriate areas. Face it, in the step before the car was chopped apart, there's nothing left, so we have to put back.  Some of the common pieces of steel are 1/2" square tubing, 1" square tubing, 1"x2" square tubing, 1/4" plate steel, 1/8" plate steel, and 1/16" sheet metal. We bought our steel at Alro Steel, and they have several locations throughout the country.

This is the finished product with all the steel.