Will a 66 drivetrain swap in to my 68??

The engine and trans will work in a 68, you just need the proper motor mounts and they are available at Mancini.

If you need the suspension off the 66, the tie rods, and sleeves will work, the pitman arm and idler arm, and k-frame are different. I'm not sure about the upper and lower control arms, I think that they are interchangeable from the early A to the later A.

The axle will work fine also, but I wouldn't waste time on a 7 1/4" axle for a 360, you'll break it... Go with something stronger...