The old "diff on the chest whilst you roll the creeper under the truck" gig has been played out by me.
Exactly the method I was going to suggest, and use regularly. With the identical diff I might add.
Oh, and I noticed a reference to a gasket. That is so.... 80s. (I make-a the funny...)
DON'T use a gasket, use a good FIPG product such as Toyota Orange driveline FIPG, or better yet, a Permatex product branded "The Right Stuff". Holds incomparably. Won't seep even after rock-bashing.