ATR .223 / 5.56mm FAL parts. Surplus from the RRA .223 FAL project. New barrel in the white, may have spot staining from storage. Threaded 1/2×28, with A2 flash hider. Surplus gas block, .223 bolt, new .223 firing firing pin, modified extractor, modified BHO, new return spring assy, ejector. Gas port already drilled. No guarantees.
You will have to come up with some form of magazine adapter. The original ATR used an alloy receiver with an AR-15 mag well, as does the SAR-4800 .223 FAL. Consider also the 5.56 Galil mag.