Joe,
I have an Eaton HO52 rearend. The differential from the Eaton HO72 should swap out. Those were made with 4:10 gears in the early 70s. There are a few bolters on here who have done it. I am on the search for an Eaton HO72 to try it myself.
I found one at eatwestautoparts.com. Just aing for them to confirm the gears before I buy it.
Rich
