Final 2 items in build 1 can be any of the following:
Shurelya's Battlesong......Support doesn't have it, need to be a little tankier
Zeke's Herald...........Support doesn't have it, not a lot of gold, team is losing (need the push into an offensive stance)
Phantom Dancer..........Have enough gold for it, game is somewhat evenly-matched thus far
Youmuu's Ghostblade.....Need that extra push to win the game
Infinity Edge...........****ing rich and the team's carry isn't doing enough damage
Guardian Angel..........You're basically the tank of the team (for those pubmatches when you have 5 AD carries...pfft...pubmatches)

In build 2 you can also start Regrowth Pendent and a health pot and build into [philosopher's stone]] before boots--particularly if you are against an AP champ top.
You can also end with Hexdrinker into Maw of Malmortius if the enemy team is AP heavy or if you need some extra attack damage instead of tankiness or even replace Phantom Dancer with it if you still need the tankiness from Guardian Angel