You can get custom heads for
IG Cadian units, that's what I have done.
I got Pig Iron gas mask heads and some others and my paint scheme is similar to
DKoK. I love the
DKoK look but the price prevents me from getting many models, and once I do get some they'd be my veterans / elites.
Its an option if your looking for infantry to use Cadian bodies and pig iron gas mask heads they look like they could fit well with
DKoK infantry.
Pig Iron Heads:
http://www.thewarstore.com/product45439.html
http://www.thewarstore.com/product29988.html
Frankly for myself I wanted to go guard but I didn't like the Cadian heads but I loved the look of
DKoK but couldn't spend that much. Once i saw the head models from pig iron I went for it. I can replace the Cadian heads use the
IG/
AM codex and maybe down the road use them as
DKoK!