Pre 1976, the D44 used a 3.73 gear ratio. In '76, they adopted using the 2.73 along with the 3.73, so you could have either one.
As for your engine/tranny combo, check out Novak Conversions HERE
They have a lot of info on early and late model Jeep engines, transmissions, and transfer cases.
If it was me, I'd like to have a NP435 behind a 360, but it really depends on if you're wanting to have this rig for street use or crawling. With some transmissions from other makes (like the Ford I mentioned above), you will have to get a new pilot bushing in order for the engine and tranny to line up. The bushings are relatively inexpensive and you can order them from Novak.
Somebody, feel free to correct me if I'm wrong on any of this.
What year is your J10? Just curious.