Some observations;
'S30-01036' would indeed be an early 1970 production (probably January or early February) S30-S Standard model 'Fairlady Z' or S30 Deluxe model 'Fairlady Z-L'. A closer look at your remaining trim and accessories should tell you whether it was a Standard or Deluxe model, but it's more likely to be a Deluxe just based on the law of averages and the stainless trim that I can see.
The G-Nose assembly, whether it indeed is a genuine factory item or an early aftermarket copy, would have been attached to the car after (probably quite a way after) October 1971. The original colour of the car looks to be #905 red, which would be correct for a 1970 production Fairlady Z or Z-L. The 'Grand Prix Red' choice on the Fairlady 240ZGs was actually #110, so a different shade. It's kind of a moot point anyway as your car clearly isn't a Fairlady 240ZG.
I don't see anything specific that would point to circuit race use in-period. The seats are aftermarket sports seats and are certainly not factory race seats, the centre drop bar brackets for the roll hoop look to be an aftermarket copy of the Nissan Sports Option items (yours appear simplified in comparison to originals) and there's an awful lot of interior re-trim with non-standard materials evident, along with a later centre console. It looks like a fairly typical 70s/80s 'street tune' car to me.
The photo of the left door interior looks - to me - to show it is a later replacement.
Does the engine bay tag match up with the body serial number engraved on the firewall?