Am I going nuts ?

[luke]

https://www.mrlugnut.com.au/lugnuts.html
Part no: 5077-1/2

The new nuts worked like a charm. 

Although I measured everything before ordering, I was still a little worried about the length of the shank so tested them without the wheels (straight back to the hub) and no issues.

Another reason I was originally wanting to change the studs was because the old nuts were a different size to the Prado, but the new ones are also a 21mm socket. (Same as Prado)

The wheels are 'lug centric', however so were the steel wheel's as fitted by track originally, so I guess we'll see how they go.  Other than that, the hub caps don't fit, but I can live with that in the short term . . .

Now I just need to sell the old wheels 

[Alien]

Good to see you've sorted the nut issues.
I'd suggest looking into making the wheels hub centric, in my case I had slip rings made up.
https://www.machinedesign.com/fastening-joining/article/21832042/whats-the-difference-between-lugcentric-and-hubcentric-wheels