20x10.5 +15 will fit, but you'll need to be careful selecting tire sizes and setting rear camber to ensure a trouble-free fitment without rubbing.
You can see the 20x10.5 +15 size on our Silver Standard Portfolio Project, originally built in 2009:
You can see more photos here:
http://www.m3post.com/forums/showthr...ilver+standard
http://www.m3post.com/forums/showthr...nging+standard