65 barracuda tire and wheel size

Hi everyone
I have just purchased a 65 barracuda and will be making a tire size change. I intend to go to 17” wheels on all 4 corners. On the rear I am wondering what size will fit as wide as can be . With what backspace on wheels also. Right now it has BFG 215/70r/14 on all corners. Any info will be really be appreciated