I am sure lots of people get plenty of
PR for an ad, but the one in question is clearly false. I have owned 8 early Porsche cars including a real 73rs and real 74 3.0 rsr and I know how they run and how they are built.
The 73"S" was a very capable car, but the 2.4"S" engine had a finite amount of updates and upgrades allowing it to have enough hp to move this car (with standard body) to get it to 165mph. It is an aerodynamic issue that would mean your car would need over 300hp (give or take a few HP) to get you there. My 3.0 RSR was good for about 180, but it was pushing over 300hp and that was based on gearing, but the aerodynamics were such that it could stay planted firmly on the ground.
Obviously, there is more to take in account than that, but the bottom line is that his 73"S" is not a 165mph cruiser. Not a chance. Physics has taken over.