612 wheels and interior

i park next to a 612 every day that has 20 inch rims. then today i went for test drive in another one, and it had 18's in front and 19's in back. i am assuming the latter is stock, and the former is some kind of after market change. i am wondering whether these were 599 wheels, or just optional 612 ones. and if you get these 20 inchers, do you have to change anything on the speedo or tach ?

the the interior of the car i drove today was crema with daytona seats. very nice, except that despite the low mileage (10k miles), the leather looks a bit dirty. is there an easy way to clean these up or do i need to give it to a pro?