Re: Gas block???
PRI still offers both the black and SS 0.875" adjustable gas blocks. I don't think they come up on the website, but they are still cataloged items for 2012. You need part number 05-875-02GT for black and 05-875-02S for stainless.
Also, give the fine folks at Paladin Machine a call and tell them you would like a 3-position adjustable block for a barrel with a journal of 0.875. They'll need your gas port size/measurement, and then they'll make one for you spec'd to your rifle.
Paladin Machine Service
3832 Gates Ford Rd.
Kershaw, SC 29067
(803) 475-7542
While they don't have a website with any pics, etc., you can find plenty of reviews of their products online. I have used them and I think that they are truly excellent products.