OK, just did multiple Google searches using various phrases, and finally found a pic of the car I'd been looking for:
But the description of this car now makes me think it possibly wasn't built from a real XR4i, as its listed as being a tube-frame and fibreglass body.........unless they're talking about just the flares and front end being fibreglass. Would be interesting to know though, as not many XR4i Sierras made it to NZ as road cars, so seems an unlikely model to create a mold for and build a fibreglass body from.