I now have a 2004 sales brochure and can verify that the runabout is described as having exactly the same mechanical spec as the 4/4 at the time, with the Zetec powerplant. Also weight, ratios, and dimensions are identical. Of course the more recent 4/4s have the Duratec, which accounts for the difference in power and economy.
The cosmetic differences are minor, and the previous owner has already upgraded most things to above basic 4/4 spec.
I have arranged my insurance through the Morgan scheme - a very pleasant surprise - and will collect the car next week ... I am rather hoping for a dry drive home with the roof down.