I have driven LHD American and European, RHD British, Japanese, Australian and South African S30s. Some on skinny factory spec. tyres but most on wider after market alloys and never noticed a difference in driving.
If you were using the car as a daily and commuting to work on the Stelvio Pass you possibly may notice a difference but not in normal road use.
Embrace the car for what it is, a US spec. car.
The more important changes to make are to upgrade the diff and box but wouldn't get bothered about modifying the rack personally.