When comparing the inner hub seals between the IFS hub and the original Hilux hub there was a difference in the internal diameter of the seal, The IFS ones had a larger internal diameter.
I went to Toyota and checked with them.
There are two different seal sizes used in the IFS hubs. The seal I had in my hub plus another seal that has the same internal diameter as the Hilux hub. Obviously you'd need to replace with the smaller ID seal.
So if anyone is doing the hub swap check your inner hub seal.
oh and the correct seal was $7 from Toyota. The thinner seal was dearer.
Correct new seal on the left, Old IFS seal on right.
Clear as Mud?