If the rifle is to be dedicated suppressed, I wouldn't worry about the OSS, and would just get whatever can you want that fits your attachment, weight, length, and durability criteria. After picking out the can you want, grab one of the Black River Tactical gas restricting gas tubes: https://blackrivertactical.com/WP/Ad...Drive-c6464009
This will be more foolproof than messing with an adjustable gas block, cheaper, and easier to install, while also turning down the gas drive to allow the gun to function better.
For something bombproof and can take mag dumps if needed, the easy button is the SureFire SOCOM556-RC2. Otherwise, if you're comfortable relying on warranty for anything that might happen, the Rugged Radiant762 with a .223 endcap would be my recommendation. That being said, I'm just a random dude on the forums that's done a lot of reading, so don't expect me to back up my recommendations with hard data. FWIW, I own a SureFire SOCOM556-RC, two SOCOM556-RC2, a SOCOM762-RC, a Rugged Obsidian45, and a Rugged Oculus.