I bought this fitting that replaces the oil cap on my LS valve cover. It simply screws on, just like my oil cap, has an o-ring for a leakproof seal, and doesn't require any welding or fabrication. It has a -10 outlet which allows you to route a -10 hose over to your catch can, or separator. Check out the link...
http://www.mtiracing.com/valve-cover...ter-to-10.html