What front axle would a 70 j4000 come with from the factory?

Dana44 I think. I don't know if its open or closed knuckle. I don't think that Jeep used a Dana60 front in anything but the M715. Hopefully someone more knowledgable about J trucks will chime in here.

Have you taken a look at this page: http://www.off-road.com/jeep/tech/jpu.htm

I think you are right.

yep I would have to agree ee...on the Dana BOM it only goes back to like 78-79 but all the other J trucks used D44s