Dinner tonight! Chicken stock for Clam juice?
I know you said "tonight" two days ago - but just in case you come back to this - I bet your chicken broth worked out fine, but next time, if you want more seafood kick from the broth, add a couple of anchovies. Looking at that recipe, I'd recommend melting them in with the onion and oil toward the end of that part of the recipe. It will give you nice depth of seafood flavor and lots of umami.