On a '70 I went with 17x8 4.125 backspace on the front and 17x9.5 with 5.5" backspace on the rear. The front came out just right. It does have "Hemi style" increased clearance front fenders even though it wasn't a Hemi car. If I did I'd again, I'd use a little less backspace on the rear - 5.00 or 5.25".

PS: Bigger wheels alone without brake upgrades may actually hurt stopping distance. Also a stiff short sidewall tire with stock suspension may not respond so well to turns and real roads. Agree do the brakes first or along with the wheels and at least plan on a set of really good shocks if not additional suspension upgrades.