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G'day John,
I have a B/W photo of '29 in flight. The prop boss appears to have been either left unpainted,or the paint has completely worn off, so a gloss Aluminium colour would fit.
Cowl interiors (including the firewall) were usually the olive or yellowy shade of Zinc chromate. Humbrol 81 is a nice match for this, though tones could vary - even within the same aircraft.
On aircraft with the 3-tone navy scheme, such as '29, the radiator grills would most likely be the off-white of the lower fueslage (will attach a pic on a restored bird)
I have a feeling '29's hubs were straight Aluminium, but I can't be 100% sure on this...some 3-tone scheme aircraft had these painted in black. Gear legs would most likely be off-White aswell (flat white with a very slight touch of black added)
Hope this is of use, maybe someone else can be more specific.
Radiator/ oil cooler: Kiwi Aircraft Images : Photo Page
Undercarriage leg: Kiwi Aircraft Images : Photo Page
More images: Kiwi Aircraft Images
Evan