You're welcome, Grannic.
As I've mentioned in one of those older threads, there was only one readily visible change to the chassis, during the HD-8 model run.
That's the front axle mounting, and yours is the later type.
The bonnet mods are a bit harder to fit into a definite sequence, e.g. the louvres used on some examples.
But I can say that the fuel tank cutout is engine-specific, not related to year of manufacture. It's only found on the G65-engined HD-8 examples, as the Fuji Robin EY25D engine [which was fitted to HD-6's IIRC, as it was 'nominally' 6hp] had a lower profile, and didn't require the cutout.
Your machine does look to be in very original condition, allowing for its age; very few dings - the leading edges of the rear guards and bonnet usually cop a few on these machines. The engine looks very original too, except for the muffler. Which is no surprise; even though the originals were made of corrosion-resistant aluminised steel, the leaded fuel of those days made for short muffler life.
Edit: And genuine replacements were always pricy - we Honda dealers used to put them on the 'monthly stock order', which had a higher discount off list price than routine parts orders.
The original rear tyres had a much 'squarer' profile, though.
Last edited by Gadge; 07/05/15 09:43 PM. Reason: add info