FYI, I found another post here somewhere discussing pre-threaded barrels on Saiga 7.62x39's, so I went ahead and used my mini tubing cutter to remove about half of my FSB sleeve. My hand and wrist started to get sore, so I clamped a mini vise grip on the knob of the cutter that allowed me to spin it with my arm. Much to my delight were some perfect, factory threads in 14x1 LH and they were clean - no rust, no gunk. I took pics if anyone is interested.
As far as the actual gas blocks go, I am favoring the AKM style that has the bayo lug at the front instead of rear. APEX has a Polish versio