9J et38 will be about right running a 245/35/18 tyre.
This is my XXR 18x8.75j et35, running a 245/35/18 MP4 tyre. I run a fair bit of camber so its not as flush a look as it could be, but it gives you an idea to go from.
DSC_0057 by Richard Beale, on Flickr