If this was mine I would not replace the sprockets as it is not cost effective to do it as per the book.
The answer to your question is that these marks are on new sprockets.
I would however definitely replace the crank sprocket.
These are the main components that I would replace:
I have the control unit and the wiring looms in stock at the moment.
However, I am fresh out of fan shrouds, but I have the fans and associated wiring and connectors.
Just drop me a PM if I can help further.
What Sim has said, get a proper 4 wheel Hunter alignment done as it will transform the handling.
The guys across the pond for once are correct, no need for a rear bar on the 370, however, I would have gone with Eibach instead of Shiteline.
Low mileage genuine Nissan preowned coil springs are in stock for 350Z DE Coupe and Roadster and 350Z HR Coupe and Roadster.
Just drop me a PM if I can help further.
These guys, local to me should be able to carry out what you require.
I have been associated with them for over 40 years and they are a well established, experienced machine shop.
http://www.agra-eng.co.uk/services/competition-departmnent
I have brand new genuine Nissan HR mid sumps in stock at the moment and good to go same /next day.
If you wish to proceed then just drop me a PM and I will price up for you when over at the shop tomorrow.