Forge world has the claw arms available, and you can use one of their Venerable bodies for it. What I did was buy two ironclad boxes. There is a "claw/clamp" arm for each one, I did some judicious swapping and got a left and right clamp arm from that. With the remaining left and right arm without "hands", I took a center piece from the same kits (looks like a cap with four cutouts) and glued skaven blades in the cutouts. Got 2 clawnoughts out of 2 kits with limited bashing.
My Storm Ravens are bashes of Shuttle Tyderium (Star Wars) and Sisters of Battle Immolators.