Welcome from Texas.Thats a nice color combo.http://www.fitmywheels.com/ http://www.willtheyfit.com/Try these calculators on for size.
Here is the questionIf I put a F6015 on a 15x8 wheel will it loose some over all height when compared with the 15x7 ? If so will it be enough to notice when on the car ?
It will not be a noticeable difference height wise, you will get a little more 'rounded' sidewall, which I think looks good on these cars.
What's your alignment? If you have an aggressive radial alignment and go back to bias plys, they are going to wear out quickly and unevenly. To utilize a bis ply, you need to go back to the stock specifications.