I would like to go 18x10 front and 19x12 rear for street tires... but maybe 18x12 can work. They make 18s and 20s? Wonder why they skipped 19?
What size tire do you have on the 18x12?
Here is the cap I was thinking of running. I have 4 that should clean up quite nicely. With your wheel style and this cap I could run my open lug w/ 3" studs under the cap and it would give it a very low key stock appearing look at first glance.
