Not sure if I'm right with this, But just from looking at the way the chaos lists work would I be right in thinking that the space marine centuries that are dedicated to the powers (world eaters, emperors children, etc) can't use the standard, non legion specific, chaos space marine cards as support detachments?

If this is so would it be a game breaking house rule to let them do so? What I mean by this is that say you are running a khornate army, with a world eaters century, and two bloodthirsters. The deamons would be restricted to the power and standard list for support cards. But the WE century would be able to take support cards from the standard, non legion specific, chaos marine list, as well as the power and standard list. So this would mean that the army could only use 5 chaos space marine support cards max, you could only get them if you are running the century to begin with.

It just seems odd that the power specific marines don't get bikes, speeders, termies, or land raiders.

From the unit description:

The World Eaters Century may take support & special cards from the Chaos Marine list.

Sorry dude, I'm going through the pdf, and I can't find were it says that.

The unit description I have goes into the fluff behind the world eaters (and the other power specific legions) but gives no rules. And it doesn't say anything on the cards.

I'm using the 400KB pdf. Is what I'm trying to find in the 57MB one?

Yup. Downloaded the 57MB version overnight. (our area is having slight broadband issues right now) And there was the line, plain as day at the bottom of all the dedicated legion descriptions.