Tire size questions

Your stock tires are approx. 28.9" tall. A 255 60 r15 is only 27" tall almost a 2" drop in height. It will help acceleration but might look a bit small in comparison. Your Speedo will be 4.5% off ready slow, 60mph will be 57mph.
You can use this website to run some tire sizes to get an idea of how tall a tire is.

Custom wheels, rim tire packages