use the head unit mount from crutchfield. there's two pieces, you only need the main rectangular one.
remove factory radio.
dremel out the little piece of metal/sub-frame/dashboard directly behind the head unit
put new head unit in said rectangular piece. (it will sit flush)
install, put your four screws in, add dash piece.
FLUSH. if it weren't -500* outside, i'd go take pictures. if you can't figure it out, you don't deserve a flush receiver.