Definitely a single radome, much as on the aircraft carrying the Phoenix or it's predecessor (the Eagle). The changes to the missile would be internal: new avionics, new and improved solid rocket motors, updated warhead design, etc. What you've got looks good to me. Since you're likely going for a longer range than the Sea Phoenix, a larger antenna would be helpful, but given the track-while-scan capabilities, it would probably work for both the Nike-Phoenix and the Sea Phoenix if you should have them together on one ship (likely, IMHO, a dedicated AAW ship).