Keg spotter here, the type of spear does not equate to all the same attachment into the neck.
There are a number of variants, 14tpi (threads per inch) is popular, and the default for tooheys/coopers kegs. Cub have a draft style neck, where there are 2 lugs on the insideneck and this follows a channel on the spear body to lock into position. That being said, you can d style necks with 14tpi, same for the S and G and U type spears.
Theres a new type of spear I was part of the project called a WS-SOS, the flat type fitting with the Draft type body on the spear. Sounds confusing, it is, it is per the customer in many instances, so with this we can make it simple. The majority of DIN (tall) style kegs in Oz (Tooheys/Coopers/Bluetongue) are 14tpi. All CUB Euro (squat) are Draft style necks.
14tpi and Draft necks are not interchangable.
Scotty