Computer game: EA's old classic
SEAL Team, playable on DOSBox had some scenarios with missions that dealt with targeting specific NLF targets.
Board game:
Vietnam 1965-1972 is a highly detailed, operational to strategic level sim that has quite a bit of detail. No idea if it contains anything about the Phoenix program.
http://boardgamegeek.com/boardgame/5620/vietnam-1965-1975Pen & pencil RPG: Revised RECON. You can use the rules for Phonix missions, I suppose.
http://en.wikipedia.org/wiki/Recon_(role-playing_game)
One could also use the ARMA2 Vietnam war mods out there and make your own missions as well.