zr2 axles are nice but pricey. I get wanting an 8.5 rear, but in my experience all the broken 7.5 and 7.625 axles I have ever seen in my lifetime have been damaged from abuse, like catching traction in a donut, or just driving like you are stomping out a flaming bag of crap. Plus the zr2 was 1/100 the 4x4 blazer production, and I bet will be easily 4x the price if you find one. just a data point.
if you are looking at blazers in salvage and are ok with a 7.625 rear, look in the glovebox for the RPO codes, rear ends are under G. GU6 is the standard 3.42, GT4 is the optional 3.73, and any ratio followed by G80 is limited slip. 98-03 blazers are disc rear.
