First the lecture... switching over to a 5 lug rearend will take the truck out of your truck. Car rear axles aren't rated for carrying 1500 lbs of load in addition to the vehicle. If you are making a cruiser out of your truck this isn't an issue. If however you are planning on loading it and/or towing, this is a problem.
Ok you knew that so moving on.
Updated brakes... are you talking about moving away from your "Huck" style brakes and upgrading to "bendix" style brakes? or are you looking for disc brakes?
Many rear ends may fit your bill. None will simply drop in, so some cutting, grinding and welding is to be expected for putting a rear end in your truck.
It's hard to give you a specefic answer as to what to look for... 5 lug rear? What lug configuration? Are you matching the front?
I suspect you may be putting a MII suspension in the front, or swapping out your 3/4 ton axle for a 1/2 ton axle.
There is lots of information about swapping rearends. Don't get frustrated if you don't get a direct answer. More detail on your project will give us a better chance to answer your question, and give you more relavant answers.
