I know this has likely been answered alot already, but I couldn't find a direct answer when I searched the forums.

My character is a level 43 Legionnaire and I would really like to get the armor of the 87th tribe. Problem is, I'm already near the end of the game (reloaded a save after beating it) and I'm wondering if its possible to use Faction armor to get it? If not, is there another way? Or am I stuck wearing my Gecko-Backed Reinforced Metal Armor.

If what you are asking is 'Do you need faction armor to get the 87th tribe armor', the answer is no.

Well I said I was doing a Legion playthrough so I don't want them vilified but I want that armor to complete the look of my Centurion.

Oh, then no.
If you nuke the Legion, you become vilified.

Meh.. Even if I kill them all silently?

Nuking =/= Silent

Oooh I didn't know about the nuking part... LOL.

Haha yeah...getting the armor simply isn't killing the wearer. It's a bit bigger than that.

To pull off what you're describing, you'd need to do it before dealing with Benny in The Tops.

You can be as nasty towards the Legion as you want prior to receiving the Mark of Caesar, since that will remove all negative Rep you've accumulated towards them. Hitting them with the Nuke is the ultimate such act, and gives enough negative Rep to send you from Idolized to Wild Child.

After dealing with Benny and leaving The Tops, Vulpes immediately accosts you and gives you the Mark; this is the only time you can remove negative Legion Rep, so you need to hang onto it for as long as possible. I always leave the MQ hanging once Ring-a-Ding-Ding is active, for just this reason; that way I can go after the Legion and NCR as much as I want if I so choose, and still have the option to get on their respective good sides later should that prove desirable.

This.

If you're on the PC you can just use console commands or one of the mods like LR unlocker to get it without nuking the Legion. Just pretend that Caesar gave you the armor of the 87th tribe for utterly castrating the NCR in the Mojave or something.

Well my entire point was theres no way I can do this because I'm way past that point so I was wondering if there were alternatives. Oh well, I already finished the DLC and went and got the Scorched Sierra Armor. Now I just need to finish For Auld Lang Syne with NCR armor on (I'm vilified by them and idolized by the Legion. Ugh, stupid Gannon) so I can wear it... Its ten times better then the Armor of the 87th Tribe in the stats department.