I have purchased some of the Antonio Masiero Italian gears and so far so good. The tranny I was woking on last night got a new italian countergear and it went in like buttah. If you really want a quiet gear set you might not want to mix and match with old GM and new Masiero but it can be done if you have to. The new supercase is real nice as well if you are not working on a number matching car.
I purchase from Paul at 5speeds.com
-Mark.