Stu Rogers of Inter Norton Spares in Wisbech Cambs and Paul Norman of Racing Norton http://racingnorton.co.uk/
are probably your best 1st points of contact.
Understand that both these folks are sorta home businesses, so may be tough to contact sometimes.
And may only be able to guide you where to proceed.
That tank is going to be expensive !!!, and the outer primaries appear on fleabay etc now and then.
If you allow that sv and ohv and ohc bits are not entirely identical, good luck !