I blew the dana 20 rear axle on my 76 cj7.  I found a dana 44 rear and matching dana 30 with lockers for a full axle swap from a 72 cj. I am was in the process of cleaning up the dana 30 front when I noticed the upper and lower ball joints had no greese fittings and the joints did not move at all.  My question was should i be able to turn those joints left and right with no tire on the axle or should I replace those ball joints.  

New ball joints should be stiff. Used ball joints out of a 72 cj should be able to move some what easily depending on mileage. Sounds like the old ball joints have rusted up inside. If you don't replace them the rust will come free and your ride will get interesting fast. I suggest replacing them now that the axles are out. I consider ball joints, seal replacement and bearing inspection to be a part of any axle swap. Either way a cheap peace of mind.