Was researching this topic recently, as I scored some vintage
Watenabes for my AE86, and found the stock studs were not long
enough to get the proper number of turns on the wheel nuts. This
is what I found...
The only useful measurement is the length (measured from under
the head) as hub thickness and brake discs can affect the amount
of stud you can see.
All of these studs have the 14.17-14.20 knurl and will happily pull
into AE86 hubs without raising a sweat. A lot of the Toyota studs
are used on more than one vehicle, and may have "replaced by"
part numbers different from the original.
Cheers... jondee86