If its 3.90s, you need to get it, no matter how much hassle is involved. I think it is probably a 4.57 if its from 63. I am not sure if you have a mudbog near you, but the guys that run here are buying up the 4.56 and 5.14 eatons to put in their trucks as they are slightly narrower, bulletproof and much cheaper than a 14 bolt FF or Dana 60 (or 70). Unfortunately they guys with jeeps have also realized a 67-72 Eatons with a 4.10 fit real nice in their "trucks", too and many have detroit lockers in them from the factory.
