help wheel fitment 1968 firebird go or no go?

[Steve Firebird]

I am getting ready to order new wheels and tires and wanted to get some input. I have searched this site and few others and came up with this plan. First the car is a 1968 Firebird mostly stock suspension but 100% new / rebuilt with polyurethane every where. It has disc brakes on all 4 corners and a 9" ford rear that is only 1/4 inch narrower than the factory rear. Here is my plan.
Front 17 x 8 with 5" back spacing and 225/45ZR17 G force KDW2
Rear 18 X 9 with 5" back spacing and 255/45ZR18 G force KDW2



Do you think I will have any issues? I found a few cars with bigger wider tires on stock set ups that said they fit OK or had very slight rubbing when driving hard so I expect what I have planned to be ok but wanted to check other that have had experience with oversized wheels. Any comments welcome Steve