http://www.hotrod.com/articles/1010sr-quick-change-rear-end/

Being able to quickly change diff ratios could answer a lot of questions similar to those in these posts.

In these days of CNC
it would also seems that making
custom planetary gear sets
to go inside Chrysler 46/47/48 OD units
would not be that hard or expensive.

Swapping OD units would just slightly more work than changing
straight cut gears in a Quick Change,
and those extra gears in a Quick change add friction drag, perhaps 2 to 4%.