Hobot,
It wasn't Hooper who introduced the Isolastics (and the diaphragm clutch) to Harley, it was his old friend and colleague John Favill.
To today's eyes the cast wheels don't look too modern, us now being used to them. At the time the cast wheel was considered "modern", and many motorcyclists preferred the spoked wheels, especially those in the market for a "classic" bike. The sentiment remains, hence typical "retro" models still sport spoked wheels rather than the- much cheaper, hence for a manufacturer far more attractive- cast wheels.
The Moto Guzzi style forks, brakes and wheels were not popular and, in fact, a cost saving exercise against Norton's own "Roadholder" type forks, AP Lockheed/Norton calipers, and spoked wheels.