9s should plug and play.
Many threads on spacers for your plans. In short, 911 8s with 245/45 can be pushed out max with 21mm spacers. You'll need 65-67mm studs. Search RoyB's post.
The spacers with push the 8s out more than actually 9s.
More negative camber will help avoid rub. I have -2.4 in the rears.
Buy the 928 21mm spacers from our host and 10 new studs... I know since I just did all this...
