I think the half-closed and half-open drive shaft you mentioned and have pictures of is the front torque-tube half of a 3/4-ton drive shaft as used 48-53. Of course you won't reuse that if you make that NV3500 or another trans work. Good luck!
(Edit) I should have looked at the pics of your truck first - it is a 3/4-ton! How did you get the 6-lug hubs/wheels on the front? (edit, again) I should have read the captions too - it has a 1/2-ton front axle, duh. And after you get that red rear end under it you'll have a longbed heavy-duty half ton. Cool.
