i have 18x7.5 rims with 45mm offset....what spacer sizes should i get? 15mm front and 25mm rear?

To make it flush with the fender lip (with a 7½" width wheel ET45), you can run a 15 to 20 in the front which will make it ET30 or ET25. On the rears, you can go maybe 25 to 30 or so. If you go extreme to the max, you should probably have the rear fender lips rolled to give you more clearance. If you just want to make them near flush with no fender mod worries, I'd go 10 front and 20 rear. Make sure you use a reputable strong stud replacement. I read a recent post where someone had a good recommendation.

cool thanks for the info!