Remember, the trick with the Richmond 5 speed isn't the final drive, but the first forward gears. I've done several Richmond swaps (non-Mopar) and changed the diff gears to something in the 3.0 range. Works like a charm. The downside is that the shift linkage takes up alot of real estate on the side of the trans and I don't know for sure where the shifter would end up in an A body.