You forgot the seafood based combinations! They have pure seafood bases too, though. My Japanese friend brought me to a shop in Tokyo that apparently specialised in a 100% seafood base/stock. It was light compared to the meat-based stock but equally good.
You will find it hard to know for sure if there's no pork though because even if it's labeled salt-ramen if you look at the details it might say made with pork as well.