You're lucky with an alto - most any alto neck will work, although there are naturally subtle differences in tone/response/intonation. I played a replacement Mk VI neck on a Selmer USA alto for years until I went back to the original neck just to see what happened, and I've been playing it ever since. It just seemed to have a 'thicker' sound, or maybe 'more whiskers' as someone said. Funny thing about that neck - when I first got the horn, it played flat enough that I had to push the mouthpiece way up on the cork, disturbing the relative intonation of the horn. I cut about 1/4" off of it and it plays great to this day, although the mpc still goes pretty far up but not far enough to get the neck up near the chamber. This was true with the Level Air I played in 1983 as well as the Guardala Studio I now use. Must be a really big bore on that neck!