Live, I'm not sure how to say this, but, what is it that you think this stock will make your Century L1a1 do that it didn't do before? Or, do you want this just because you think it makes the gun look more evil (and different from everyone else's) and you are willing to spend $300 to make that happen?
I'm not saying that the second choice isn't legit... I want one of those idiotic 37mm flare launchers to put on my M4gery. Why? What can I legally do with it besides make my own super-expensive, labor-intensive flares that probably won't work half the time anyway? Its basically $200 for something that looks like a badass M203 but is useless, and there's no real shame in it. Just recognize that you are paying $300 for a plastic piece to make your $500 parts gun look more like a $10,000 rifle. If you can accept that without apology, do it!
EDIT:
P.S., I want this FAL, in particular it's barrel. I swear I could take on the entire Soviet Block with that thing as long as someone kept feeding me 20-round magazines...