Dont get to discouraged, here is a Dart running 18x9 Enkei's with 275/35/18's all the way around. It can be done, it has been done. Just dont freak about a little bit of spacer in the rear. No big deal, I have to run a 3/8 spacer in the front, and guess what, it is fine as frog hair.
http://www.protouringmopar.com/attachment.php?attachmentid=3795&d=1395715152