That is the same tank I have. Pull the ring off then pull the foam out. If in good shape, reuse it. As stated earlier, take the tank out and wash it out. Reinstall foam and you're good to go!

67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......