This looks like it would be a good start for you, but it's bolt together. Bolt together rollcages are a bit dodgy in my book, if you want strength they need to be fully welded. Since you have a Ghia though, I haven't found many good cages for a Ghia. I forgot that Ron Lummus Racing sells complete tube frame chassis for a Ghia.
http://ronlummusracing.com/Race_store.htm