Gears & Axles - Quick Question!

I'm getting a new carrier/gears installed in a couple days. I have my bottle of posi additive, but im not sure what gear oil to get :confused: Should i get the GM rear end fluid or should i just go to autozone and get any old gear oil, if so what brand if any inparticular and what weight? 85w-90 right? Thx 3.73's here we come :devil:

GM gets a fortune for their synthetic gear lube, if I remember correctly about $32 per pint and you need 2 for a refill. I used Mobil One and got it at AZ for ~$8 per pint. Just add the posi lube to it and you should be all set.