KCDDUSK.
The S-300 is a land-based Surface to Air Missile, you should use Annex S. You will find that the S-300P is identified as a SA-10a Grumble, while the S-300PS is the SA-10b Grumble.
Annex D has ship-based missiles. The only Grumbles I can find in my Data Annex are the SA-N-6 a/b/c series. When looking at the NATO reporting codes, remember that S = Surface, A = Air, -N = Naval (or ship based).
Cheers
Edit: The acquisition and tracking radars for the S-300P/PS are also found in Annex S, p. S-2
