I've never heard of AK's factory chambered in .35 rem!>? not sure i even belive it without seeing it. You can feed a few rounds of .35 rem in an ak47 mag if you load to a shorter OAL or reload using short round or flat nose 9mm bullets (not spitzers). As well the case head of .35 rem is small enough to fit the 7.62x39mm bolt face.
It would make more sense to me to convert a Saiga .308 to .358 winchester, shooting bullets twice the weight of 7.62x39mm (125 gr) at the same velocities as 7.62x39mm (250 grn at 2200FPS). As stated above .358 win is made from .308 brass so the mags and bolts should interchange. Could make for a VERY potent subsonic platform too.