I did mine .The most important thing is do not mix up the shims.
Is your bu a 78 ?the 78 had a big pinion bearing. the 79 and up is the same.First take the pinion nut off. Jack up the rear of the car and support it with jack stands. remove the tires.under the car remove the dif.cover rotate the carrier untill you can take out the bolt that holds the pinion shaft in.push the pinion shaft in a little and rotate the carrier so you can take the pinion shaft out.Push the axles in so you can remove the C clip with a magnet.Pull the axles out a little.remove the four carrier bolts and retaining caps (dont mix these up).With a prybar or a long screw driver pry out the carrier keep a eye on the bearing shimes.With the carrier out, slide out the pinion gear.I would change the pinion seal.Look at the two pinion if yours is NOT a 78 they should be the same size,also check the posi bearing.If all looks good install .Install the pinion then the drive shaft flange and nut .Now put the posi in with the bearing races that came with the posi and the shims that came in your stock rear end.screw on the carrier bolts and caps ,troque them to 70lbs spin the carrier to see how it spins,No binding.Slind in the axles with a magnet install the C clips. install the pinion shaft then the long pinion shaft bolt.With a new cover gasket install the rear cover .fill with one tube of posi lub and gear oil intill it comes out the fill hole. Replace the fill plug ,remove the jack stands and lower the car .Take a road test if it dont howl your good if it howls have a garage look at it.Hope thats everything.