I have a 1972 charger with air shocks that I just got 17x7 inch rims for it what would be the best/biggest tires I could put on it. I would like to go as wide as would look good on the back but they are 17x7’s as well.

 

I suspect you will be limited by the width of the 7" wheel and tire availability.

 

Yellowj -

Iowan is correct about the 7" wheel width being a limiting factor.
The air shocks are or can be a bit of a concern as well, for both tire diameter and width.
Air shocks can leak, and you have to consider clearance with the shocks fully deflated and expected spring travel.

I used to use air shocks a long time ago, as a poor man's way of suspension tuning, and it worked, but I used a 28" tire and it would pass a worst case scenario.

Archer