Well, if adding weight to the back to get 50/50 is all that you're concerned about fill the trunk with concrete.

Yeah, I know foolish, but putting a heavy rear suspension in to accomplish the same goal is about as foolish too. Now if the heavier rear suspension markedly improved the handling and ride, and that is the question at hand for an E body here, then go for it.

But less weight generally helps handling more than increasing weight.

I don't know where y'all are finding prices and weights, but the picture I see doesn't show brakes or shocks or springs, which will add to the weight. I also don't know why one would compare it to a stock Dana 60 setup either, not what I'd choose in a handler myself. In fact one could make a very cogent argument that the 8 3/4 is a better choice to ease gear changes for different type races and lighter in weight and most like more than strong enough for a handler.