I'd heard Kurtz and Lucas had commissioned a cgi X-wing test shot during the making of Star Wars, and that we have our beloved model shots only because cgi was at that time way too expensive. Here's footage of a 70s X-wing cgi test - from 1978 according to the documentary, but perhaps it's the very one produced during the Star Wars production. I don't think it's been posted here.Two minutes in:
Star Wars, visual effects, part 3 of 3 - YouTube
By the way, the first 2 parts of this are also well worth a look, despite the bad picture quality. Jon Erland speaks, plus we get Richard Edlund referencing Marshall McCluhan!