There was some discussion on this not too long ago in the "Basses" section of the forum. I cant look it up at the moment, but I
want to say that the SX neck pocket is (if memory serves) a bit bigger than a Fender (or Squire) neck.

Again, I'm not positive, but I seem to recall reading that. On a side note, I know someone put an Ephiphone/Gibson neck (4 in a row keys) on an SX. Check out the basses section......I think it was in that massive Essex thread.