All 5 of the Grand Sports were at he Cincinnati Concourse de Elegance in early 2000's. Somewhere I have pictures. A local guy owned 1 of them, he started Cincinnati Microwave (makers of Escort Radar Detectors).
If that GT 40 sold for $7mil, that car has to be 2X that, easy.
I think the twin cam heads wer pretty big but the engine was pretty small displacement. Never drove one but I don't think they were super performance cars. But people were buying 4 cylinder cars after the gas crisis. I tried selling a MG Midget that was converted to a race car in ~1974. I got calls from lots of people looking for an econo-box. Car had one seat, didn't have an interior, a top but did have a roll bar!Cosworth Vega, looked one over once, 4 cyl engine looked huge to me.
EDIT. Okay, I guess it was pretty big.