Let's just clear up a couple of points...the Bathurst 1200s were based on production cars, they definately did not just get plucked from the production line and have the hot bits dropped in. In 75 I think the car John Boston has was specially ordered from Datsun Competition(now Nismo) to do the job at Bathurst in 76. Those cars were extremely well engineered and to be honest highly illegal !!Though in their defence many other teams were bending the rules as well. The engines remained the property of Datsun and were very special. The valvetrains were ultra light and the metalurgy used was highly advanced for the time. I have no doubts they were seeing the revs quoted and possibly more. I personally have revved A12s to close to 10,000rpm and the crank hasn't dropped out! The old timers like Bert and Vixen obviously have a bit of knowledge accrued on these cars and slowly the answers to the "how did they do that" ,that we all ask ourselves are getting answered.I have been researching the factory cars for many years and have even talked to the President of Datsun Competition at the time and he was very reluctant to even now divulge details about those cars and he knew them well. As they are still highly regarded in the organisation. I have a 1974 Datsun build manual which details in very fine detail how to build a 1298cc A12 with factory crank etc to produce a reliable 135 hp. That is without the sodium filled valves and titanium rockers the works cars had....as well as special build pushrods, followers etc etc...