Both the SKS, the CZ858 and other AK variants have sights that are set for their ammo's trajectory. When properly sight-in, you can use the corresponding sight settings and use a 6 o'clock aim for the distances you want to shoot.
However, bear in mind that these rifle/sights and ammo are designed for short to medium range combat purposes, while you could probably shoot better than expected at long ranges such as 500m, they are not the best for long range shooting.
Also in Service Rifle competitions such as those held at the Volkes Range in Chilliwack each year, your SKS/CZ would not be competitive against others using ARs equiped with scopes and match ammo.
However, a while ago, a friend showed up at the annual BCRA Service Rifle match with a stock M1 Garand, while he wasn't competitive, he had a ball.