Except the Opel was front engined, wasn't it? At lease the Fiero was a mid-engine design. The Opel was a much better looking car, though (IMHO)!
V-8 Archie produces a GT40 replica using a SBC where the Fiero 4 banger was. I predict it would be a wild ride! You can check out their GT4T right here:
V-8 Archie's GT4T
The V8archie GT4T is represented as a "...totally accurate Mk I body..."--sure looks more accurate than that one in Lynn's original post. You decide for yourself, I guess.
As for the styling, I, too, think it's far enough off that it's a no-go, too. Still, for those for whom authenticity is not important and who are willing to accept the obvious styling differences, one of these might just be the ticket. As far as cost, I think they are much less than our 40's--never cared enough to investigate that issue.
Doug