G'day Dr Andrew,
The Amilcar engines are overhead cam as far as I can tell but good luck finding one anyway, I sure as hell wouldn't hack one out of a full car, I do have a small conscience. The Renault engine below would be perfect.
Here's a pretty little DOHC Alfa straiģht 8 I took a photo of at Amelia Island. Can't remember the model but this is the inlet side, you can see the supercharger tucked away down the bottom, finning galore.