I guess it's possible that a non Z Blazer could have it. It would be the 59" axle, though. If you can get the 8.5" that's gonna be better than the 7.6" for sure

 

Have them send you a photo to post that shows the axle tubes - I'll ID it as a 7.5 or 8.5.
7.5 will have same size from backing plate to center of housing.
8.5 will step up size significantly just before attaching to the center housing. Zoom in on this photo and look.

 

[QUOTE=LesMyer;703615]

that's a nice rear end you got