Well there are the Ford 9", Ford 8.8, GM 12 bolt, and GM 8.5 which are all popular upgrades. The stock rear with a little bit of upgrades can hold up to about 400-450 (i said with upgrades) With a powertrax carrier, girdled diff cover are good enough upgrades. But traction is what breaks these rears. I had a 87 SS with a 357 sbc and a 250 shot that use to run high 11's years ago and with those upgrades it held together for 2yrs untill I sold the car, I do not kno where and how it is doing now bc its been about 5yrs since I sold it but the stock Gov lock held up to running mid 12's with a 355sbc and a 150shot. Only thing that blew on that was the locking clutches so it would lock and unlock making for a scary ride.