18'' wheelo fitment

You would be better off going 17's in the front as you will have more tire size choices.

Check into tires before you purchase your rims to make sure you can get matched sets.

You will see that there are not many choices for 18's.

I'm no expert, but I must disagree with that statement. At this point, I believe there to be as many, if not more choices in 18 than 17.

I do agree though, check your backspace measurements many times over. I'm not doing a stock rebuild so I don't know what will fit, but when I was considering doing an RMS conversion up front, I was looking at 18x8 with the standard Mustang back-spacing.