as much as anyone hates to be wrong, i think i may have been wrong.
I think the 63's were infact original freighters. If my feeble memory serves me, they were the box stock Douglas freighter straight from the factory, no wierd mods or panels in the cockpit.
I know some of the guys that had to evict a family or two from the airplane while they were living in it, in Zaire before they could fly it out.
they were capable of (i think) 110,000 pounds of cargo.