FR 500 wheels for my 2000 GT Convertible

I am considering new wheels and tires for my 2000 GT vert. Im looking at 18 x9 FR500 in anthracite (my car is zinc yellow with black stripes-Spring Feature car).

Nitto 555 tires.

I havent decided what size to go with, I have a few concerns.

1. I take this car on long haul vacation trips and it is heavily loaded. We run from central Pennsylvania to Myrtle Beach every summer. Soooo.... I have the need to rotate tires to get some miles out of them. I want to buy the same wheels for front and rear.
2. My car is currently at stock ride height. Im thinking to lower it an inch in the future. I cannot have a rubbing issue anytime.

So... how much tire can I get away with and not have any rubbing issues with these wheels??
245/40 18? 255/35 18?

Is this too much rim and tire for the car? I dont want to mess up the looks.

Thanks

Jess in Pa.

Looks great! Any rubbing issues anywhere? And thankyou for the pic and reply.

Ok, now I need to find a dealer in the next few weeks who has them on SALE. The bigger Mustang houses seem to have them at their everyday regular low prices, but no sales at this time. Does anyone know who is really offering a deal on these right now or in the next few weeks?