It's just a couple of weld points i believe. Should be pretty easy to take out.
The earlier ATI MKE have different style carrier block than the Zenith MKE, but do the same thing. Even the SP5K will keep the F/A carrier from being inserted into the receiver except it has a small pin at the top of the receiver.Wow, really interesting read. Do carrier blocks differ between Zenith versions? Does the SP5K have a block as well?
The ATF is such a mystery.