Sorry to get into this Abbot&Costello routine so late, and I wish I could keep it going,...but I'm no entertainer.
Your manifold nuts would have been cadmium from the Factory.
Modern reproductions have had a funny green tinge lately, and one set that arrived unpackaged I swore was zinc. Then an identical set from Colony arrived, still labelled as cad.
So if you want an authentic finish and want it to age appropriately, you must go the extra mile and have your own finishers plate your hardware.
(If anyone knows a plentiful source of top quality cad manifold nuts for H-Ds, let us know!)
As far as the body finish of H-D Linkerts, enamelled black is dictated. Drippy black is what I have found on unrestored units, but they weren't H-Ds.
Your manifold matched the nuts with the same plating.
If I am to recondition the manifold, please do not have it plated beforehand!
Beware! The spigots of WR/K are comparatively thin and and most prone to distortion form overtorquing, or just falling down upon them. I routinely must attempt to swage each spigot back to a reasonable outside diameter before I then lathe-cut it back to true-and-round. This takes and extra ten minutes ($10).
Lathe-cutting the spigots true is twenty minutes, same as a T unit. Grinding the flange to flat is five. Any blast prep is another five. As a courtesy I prep the manifold with a gas-proof isocyanate urethane that closely mimics cad (or add bronze powder to simulate nickle as needed.) It will inhibit rust but not plating.
Then, after all that, I can custom-fit a pair of PEEK seals for $60.
Return shipping in the USA averages $8.50; I cut on Sundays and ship on Mondays.
I thank our host for allowing this shameless self-promotion.
OH yeah PS:
Chromed units are scrap. Don't send them unless you can endure a stiff penalty.