Variable numbers, depending on the purpose of the clone. Usually, yeah, a full head, though.
But, you’re mistaken about the difficulty of pulling implants without killing the brain, Dr. Valate. People can destroy and swap out cranial hardware pretty easily, and routinely do. The main reason I (and probably most people who don’t) usually don’t is economy, real or perceived: it seems wasteful to destroy something that expensive, even if you no longer need it for any purpose and have something better to stick in its place.
I have a jump clone I can’t remember ever having inhabited, basically because I can’t stand to strip out a head full of Improved implants. It doesn’t do anything for me in the moment, like help with armor effectiveness or shield boosting, but it’s also too expensive to risk in a high-risk combat op. So there’s really nothing I want to do with it. It just sits there.
Meaninglessly.
Sigh.