Happens to me a lot too! Especially with the current medication...

As far as the swap to a firebird axle goes, IMO it is not worth it. As mentioned, you would have to cut off the mounting brackets and weld on spring perches. The axle innards may not be the swappable either depending on what the firebird originally came with. There are a few different sizes of 10-bolts.

 

I have a 95 Trans Am, it is the same 7.5" 10-bolt as the S10/Blazers, and can tell you that the rear is wider than a stock Blazer, although I believe it is the same width as the 8.5 in the ZR2's. You would have to cut off the shock/spring mounts off of the Firebird rear then weld on Blazer mounts, check to make sure the tubes didn't distort any during welding and then still need to check the brakes to see if they would work. The difference from 3.42's to 3.23's is not worth it especially for the LSD, it's only about a 5% difference in gearing about the same as switching to 30" tires. If all you want is a limited slip, just find one someone has pulled from their F-body and swap it in or swap in the diff from that rear. Much easier and less work.