Not sure how well these might fit..anyhow a good deal for brand new set of NT01's from discount tires eBay site. $816 after discount codes AND free shipping.
http://www.ebay.com/itm/2-NEW-275-35...item4861ad669b" rel="ugc" target="_blank">http://<a href="http://www.ebay.com/...4861ad669b</a>
245's would be ok for a 328 if you have a 335 I wouldn't do it unless its AutoX (quicker to put heat in the tire) and not HPDE.
I had no problem with 18x9.5 rims with 45 offset (using 12mm spacers up front) with no camber plates. I took the GC plates off and sending them back.
I'm running another brand of plates (prototype) but as it looks your setup might not need the clearance.