All the Jag alloys fit -- don't see the point...

Surely because you get to keep the period look you'll lose by fitting the Jaguar alloys. The ones pictured (HRBB Porsche?) are closer to standard but the holes aren't the same size or shape.

...duplicate...

Indeed. Idea is to have a modern wheel while keeping the hubcaps. I've been looking at suppliers but there doesn't seem to be many - your ideas welcome.

Ps: pics are indeed Porsche look alikes from alloyreplicas.com