How many wing attachment nuts are there on a DC-3/C-47?
Information on PPRUNE (without a source) says:


  328 per side (102 x AN4-7A &amp; 226 x AN410A bolts to be exact).


I was able to verify the 328 figure from various books.


  Each wing of a DC-3 transport plane is fastened on with 328 nuts and bolts. Unless the stress and strain are distributed equally, some of the bolts shear off. The answer was found in Elastic Stop Nuts. These nuts can be given precisely the right tension—then lock fast. This is one of the important structural fastening jobs which Elastic Stop Nuts have solved.


(American Aviation - Volume 7, 1943, p.82)

I tried to find more info, to no avail.