So if you are looking for a stock limited slip..look in all the Camaro's, Trans-Am's ect. of the era to find a used one. They are not too hard to find.
If it is a dirt track only car you can just weld the spider gears making it act like a spool.. Not the best idea but it will work. But yes you can swap the carier and gears out without removing the housing. It isn't just a bolt in thing though you have to know how to set the rearend up