I have a 96 blazer 4x4. Rear end is shot. A friend has a 98 s10 2wd will they interchange? Thanks in advance.

 

Most probably - NO.

Needs to be the correct gear ratio, correct drive shaft flange and brake, handbrake and brake lines.
Should be possible to find the correct one in some wreckers yard.
Use the options list in your truck and the VIN to figure the correct ratio.

 

Just to add to error_401's answer, the 2wd axle is also 3" narrower than the 4x4 axle, so another reason why that wouldn't be a good candidate to replace yours.

 

What is wrong with the rear end? You can get a center chunk and if your ring gear is not shot swap the ring gear to maintain gear ratio Re-use your shims and check backlash.
Worst case, new ring & pinion gear, new carrier bearings, New pinion bearing and seal, new axle seals.
I ended up replacing everything because I installed a G80 locking rear end and had to get a Motive Ring and Pinion Thin Gear set to keep my 3:08 ratio. I had never done this before and i have thousands of miles on my rear end..