I don't have Max, so Sword Master works. He can provide a reason to have Ghost Rider in the deck when Blackcat doesn't show up before turn 3, and he's also an above rate 3 drop. I have been using Sword Master in my other Sera Surfer build as well (in lieu of Max) , and I usually try to hold him for the turn 6 miracle play to mitigate his downside, but it feels like his "downside" could be used well here.
Crossbones is part of the brew as I felt I needed another 4 drop stat-stick to justify Zabu being there. It's definitely possible that a tech card like Enchantress or Shang Chi would be better, gonna try out both.
Other than those choices, the rest is a pretty standard Surfer deck. Brood, Storm/Jugg combo (just got Jugg today!!! 5 pool 3 cards left for me), Domino for initiative, etc...