When you say running gear do you mean hubs.
This is the Andover Norton page for the Slimline Featherbed for singles and twins, this version of the Featherbed was introduced in 1960ish. So used for all 750 Atlas.
Andover Norton Parts created from the original drawings.
andover-norton.co.uk
and the page for the hubs
Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk