Rear end swap

Get a rearend gasket and smear it with gasket sealer like any other gasket. Use the recommended gear fluid at a parts store and if it has posi, use friction modifier which is a small tube that goes in with the regular gear oil.
 
hypoid gear lubricant sae 80 or 90 and 4oz.of ford friction modifier (C8AZ-19B546-A) or equivalant.axle holds 3.75 pints. buy a gasket at an autoparts store costs about $5 and use sealant like smockdoiley said
 
Or if you use synthetic, most of those have friction modifier added already. I never use a store bought gasket. I just use the black rtv gasket maker. That is what my builder uses and that is what I always do.
 
Redline makes an awesome 80W90 Synthetic Lubricant with just enough fric. modifier added too it...I ran it in my old 8.8.
It's better to have not enough fric. modifier then have too much added in the rear end. To much fric. modifier will cause the clutches to slip and the result will be one wheel peels all over again.