Swapping for an OD 904?

I couldn't find any threads in the search about this.

I was considering finding a later overdrive geared 904 for my slant equipped '74 dart swinger, since they can be found in the various slant trucks around. Are there any real benefits to this? Has anyone else done this, and if so, any real performance upgrades?

This was just a thought I had that could be done relatively cheaply and easily.