The best paper I have found for writing with a fountain pen in a notebook is Maruman Menemosyne.
I am lost without these notebooks. While I have a bunch of Moleskine books around, I think the paper is merely OK for use with fountain pen ink. Maruman Mnemosyne has been sucking up ink, not feathering, pooling or ending up all over my hands and arms.
I prefer Noodler's inks but this paper works fantastically with everything in my collection. Pilot, Parker, Mont Blanc and Noodlers.