I was wondering if I could put a rear from a 1997 Chevy blazer into a 1996?

 

Yes, but you will need to make sure you match gear sets if your Blazer is 4x4. If one is disk brakes and the other is drum you'll also need to change your park brake cable. Also, make sure that if your truck is 2wd you get a 2wd axle, or if 4wd get a 4wd axle, or if you have a ZR2 you need a ZR2 axle. The axles are all different widths.