Just to clear up any confusion:
The SKS is NOT an AK. SKS stands for "Samozaryadniy Karabin sistemi Simonova" or 'self loading carbine, Simonov system.' AK stands for Avtomat Kalashnikova. The SKS prototype was tested in 1945, against the Germans in WW2, and officially adopted in 1949. They are still in use as ceremonial weapons.
There are after market stocks available for the SKS to make it resemble an AK-47. Also, you can take off the integral box mag, and use detachable mags. So an SKS could be made to resemble an AK-47, but they are two different firearms.