Kent, Speedway led the parade to the dark side; they have purchased the rights to numerous US conceived and manufactured products and have sent the manufacturing offshore. Your statement implies that neither Jegs nor Summit is a "good American company", which is not true. All three are US corporations with similar business models, although with emphasis in slightly different areas.
As far as building a cage, I'd seek out a local late model or drag chassis shop and see if they could bend your tubes. I'd also use 1020 DOM tube, but ERW is legal for SCTA construction. vic