New to A bodys, could anyone help me with the million questions I have

Aahhh Yess!!! Another '66 Barracuda saved from the ravages of the almighty crusher.
I got my floors from autobodyspecialt.com, I believe they also have lower rear quarter sections that include the wheel opening.
'66 parts are out there, you just need to be diligent and patient.
Good luck with your build, start a thread of your restoration so we can follow your progress.