I own a 1999 3800 Camaro with a open diff and I'm interested in swapping in a limited slip differential is there any cars or trucks I could take one out of that would fit in my rear axle (eg. blazer, caprice, etc.)

 

Camaro SS the Z28 has the LSD too

 

I highly recommend all 3.8L owners do this mod -- I love my car a lot more since this change -- it really makes a difference. This would also be the time to goto 3.42 gears, if you don't have them already.

Check eBay and craigslist for the carrier. I bought mine from the former.

Also see this guide:
Carriers

 

I know that the SS and z28 do have them, but I have yet to see one in a junkyard

 

Parts cars on Craigslist

 

Gmc safari, chevy astro, blazer, s10, Sonoma, theres a few more just can't remember the names. But not all of these have the limited slip in it. You'll have to look at the prosuction codes or pop open the cover.