I built the 3" splitters along with the 3" exhaust system for my GTO, all out of 304 stainless steel.
Here's set of 2" 304 stainless splitters that I fabbed up for my '64 LeMans convertible:
If you have the skills it's really not all that difficult, using stainless steel eliminates any need for plating. That being said, our sponsor PY sells some very reasonably priced splitters in many different tubing sizes and styles that can make life a lot easier.