I would be surprised if any repaint was the same thickness as the factory paint even on bare metal.

The first reason being is many people run base clear on their repaint. So you have at least one extra layer of paint. Painters also tend to stack layers of clear so there is room to cut and buff the car. Also most decent painters spend a pretty good amount of time trying to get the car straight and smooth. That means lots of buildable primer and filler which adds thickness really quickly. These cars never had paint stacked on them in the factory like that. It would be interesting to get some readings off of cars like mine (if I ever get it sprayed) or Wheee's or Grannyknot's if it was bare metal to see what our finished paint thickness is

I plan to do a single stage paint when it's time on my series 1.  Base clear looks odd to me on a z.  The single stage, makes it look authentic.  

8 hours ago, duffymahoney said:

I plan to do a single stage paint when it's time on my series 1.  Base clear looks odd to me on a z.  The single stage, makes it look authentic.  

Oh, I agree, single stage is the more authentic looking paint but not as forgiving. BC/CC is more forgiving and easier to touch up. I will be running BC/CC on my Z for that and other reasons

I'm know E31 aficionado but mine has spent some time at a machine shop. Bigger valves were put in and the bottom was skimmed for true flatness. 
Mine...

The "31k" cars...

 

Forgive my ignorance but what do you see? Is it a skimmed head? Comparing yours + the auction one and Zadheads, is a little lip that I can see on Zedhead’s photo. Is that what you are pointing out?

I'm know E31 aficionado but mine has spent some time at a machine shop. Bigger valves were put in and the bottom was skimmed for true flatness. 
Mine...

The "31k" cars...

 

Forgive my ignorance but what do you see? Is it a skimmed head? Comparing yours + the auction one and Zadheads, is a little lip that I can see on Zedhead’s photo. Is that what you are pointing out?

The E31 closeness to the bottom edge makes me think the 31k head has been cut too. Mine doesn't look as close as that one and it definitely had a cut. Could be the angle of the photo though so it's just a guess. Like Zed said "Dog pile on". Everyone is piling on so I thought I would join in too.

 

I had exactly the same thought about the photo distorting what you can see, but also I spotted a very subtle lip on the zedhead photo. [emoji848]

Either way, I just can’t imagine that there is any chance the true mileage is a mere 31k.

Things seem back to more normal in early 70's Z auctions.  That rejected $111,000 bid....

https://bringatrailer.com/listing/1971-datsun-240z-155/?utm_source=dm&utm_medium=email&utm_campaign=2020-10-26