Hey Mario, if this don't keep you up at night worrying, nothing will!
http://www.chevytrucks.org/tech/rear_ends.htm Everything (almost) you ever wanted to know about changing rear ends on a torque tube AD. I will add to this that the 10 and I think 12 bolt rears out of 81 to 90's full size four wheel drive Chevies can fit in there with some metal working of the perches. They are about an inch and a half wider than original.
Consider the 3.55:1 replacement set of Patrick's ring and pinion for your torque tube. Total cost for everything to install is about $700 give or take a few bucks, and with a new Oakie Bushing and ball housing seals you really can keep your original setup and save a lot of headache.
