1) Does anyone recognize this spindle/ caliper combo?
2) Some say it will work if (in my case) I put 76 upper and lower ball joints in my 64 control arms. Some say it wont or are not sure since the lower control arm is not right.
3) Am I best just installing the entire crossmember? This seems like a daunting task to me.
4) Do i need the sway bar?
New airlift 2600s are waiting to go in as well so id like to do thing in the correct order and not mess with it twice.
1) You said that the setup was from a 76, so I guess I don't understand your first question. It certainly looks like the spindle and calipers from a 76 to me. I did a swap to 79 C20 entire crossmember on my 66 C20 and those look identical. But I am no expert, I only have experience with one swap.
2) I don't know about the mixing and matching of the ball joints, which is a part of the reason I did the whole swap, it just makes life easier ordering parts later.
3) I've already said I replaced the whole crossmember, so you know which way I am leaning on this one. It can be intimidating, but if your engine is out (which it probably isn't since you didn't mention it), it is not so bad. It can be swapped with the engine installed if you support the engine somehow. Do a search for a member named Hilander, he did it this way. VERY good pictures and helpful thread.
4) you don't NEED the sway bar, but trust me, you WANT the swaybar. It makes a HUGE difference.
As for the bags, I have never installed bags on the front, but from what I have read, you will need plates for the upper control arm, cups for the lower control arm, and all the associated air fittings, lines, and air management system, whether that is Schrader valves or a compressor and its controls.
Member way2lo2 did a thread some time ago about their budget install that took a day and cost just over $1000, you should search for that.
Sorry I can't answer everything for you, but this should get you a little ways down the road anyway.