/6 with 4 Speed OD, rear gear recommendations?

I have to second what Orv says.

I have an 833OD from a 75 Dart Sport, my OD ratio is .73

Running a 4.10 rear gear makes my car very quick off the line... and when you go into OD it is just a shade under a 3.00 gear ratio... decent for freeway cruising.

Besides that... turning a ratio like this saves the 833OD from being "torn up" because it no longer "lugs" in OD.

It seems as though the factory gear ratios originally used in the cars equipped with the 833OD were installed for strictly mileage purposes... and the "lugging" experienced while in OD was the cause for these transmissions getting a bad rap, because the stress was too great for the aluminum housing construction. Using a 4.10 (or a 3.23, 3.55, 3.73 or 3.91) vs a 2.45 gear makes a world of difference in these transmissions reliability.

You can also have the aluminum case bushed so it will not wear.