We seem to be making good headway, Sharon. As you no doubt have found, the 483d Anti Aircraft Automatic Weapons Battalion is listed in the TO for Fifith Amphib Corps at Iwo Jima (as part of 138th AAA Group).
Many of the WWII outfits had vet associations. From info found online it appears the 483rd did so. In an online listing I found this contact:
483rd AAA AW Bn Mr. Eddie L Bibbs 112 Rescue Rd Union GroveAL 35175-8100 Phone: 256.498.2612
I did a reverse lookup on the phone number and it shows an "E. Gibbs" at that address. It appears, then, that the listing above may be a typo: "Bibbs". I have no way of knowing if Mr. Gibbs/Bibbs is still with us, or if the group is active. However, it might be a lead you would want to pursue.