take the wheel off, and hope you can find it on the inside lip of the rim. if not ask someone with a prelude that knows. what year you got? i've got a 35 offset on the rims i have now, the stocks were 40 or 45 (whichever the civics have) and the wheels are flush with the fender, looks pretty cool.
edit: my plus signs for the offsets didn't show up?