Between the two, I'd go with a Chinese SKS. It'll be shorter than a Yugo (unless you remove the grenade launcher). Also, the chrome plating in the bore will protect it in a less than ideal environment, since you're specifically asking about this as a truck gun.
I've owned a pinned barrel Norinco SKS since 1988. It's a very reliable, rugged weapon. With the right ammo and shooting from the bench, it's capable of keeping them all in the black at 100 yards. The limiting factors are the trigger pull and the sights.