I'd grab the M1A. I'd more than likely have a handgun with a light on it for indoors and low light encounters. While not ideal as it's set up, I prefer the M1A because I am more confident in it. Even though I have far more actual training with the AR than anything else, and far more time with an AK than anything else, since I bought my M1A, it has quickly become the first rifle I look to for just about anything. I'll more than likely be using it for hunting season this year, in fact. The controls are very instinctive for me, it points like a dream and has excellent ergonomics, the sights are outstanding, and the trigger is very good. This rifle works with me to produce hits like no other rifle I've ever used, and it has better shooting characteristics too. It just feels solid. And not having that annoying buffer tube going "SPOING" next to my head all the time is definitely a plus. The rifle is heavier, as is its ammunition, which is why I can't carry as much of it. Nevertheless, I think I can work around this. The 7.62mm takes less ammo to accomplish the same task. And sense I am not going to be doing a lot of suppressive fire, I feel like whether it is disabling a vehicle, hitting a known threat behind a barrier, or whatever, I can do more with less. Plus, I know I personally have a much higher hit probability with my M1A than with either of the other two, and the 7.62x51 should be easier to find ammo for as it is a domestically produced cartridge used by our own military and police forces, and as a popular sporting round.
Runner up would be the AK. I feel like it would be less prone to breakage and require less maintenance than the AR, and ammo would be easier to find for it than the 6.8 SPC. If the AR was a piston gun in 5.56, I would probably opt for it. But as it is, AK takes second.
As stated earlier, I ain't buggin out unless I have to with that stockpile. At the very least, I know I have two friends with me to take the other two rifles.