3/4 ton rearend under a 1/2 pickup, how hard is it?

It happened again....this little twig that chevy likes to call a readend is ****ed again. I have replaced the rearend 5 times since I had the truck. I really don't feel like replacing it again but I need my good truck to make money, and my 2nd truck is on its last leg with 312,000 miles. I was just wondering if anyone here has put a 2500 3/4 ton readend under a 1500 1/2 ton pickup. I do alot of towing and hualing and replacing a rearend is alot cheaper then buying a bigger truck. I know anything is possiable and one could modify anything to work but i just want to know hard would it to be to put a 3/4 rearend under a 1/2 ton pickup. The GM factory rearend that came with the truck is a GU4 and thats the one I keep putting in it. I don't really overload the truck it is just hauling stuff all the time...Im thinking the little POS rearend cant take the heat. My truck is a 91 Silvy. Can anyone help?

Its as simple as unbolting one and bolting in the other of coarse you may have to do one of a few things cause if my memory serves me correctly the yoke on the 3/4ton is larger then the yoke on the 1/2ton so you have to either swap a smaller yoke into the rearend or buy a new driveline to fit you can also get u-joints that are two different sizes but I would not suggest using them. Then if its 4wd you have to make sure that your front and rear diff gears match. good luck hope this helps!