URGENT...firm up GTO rear

ok, i seriously messed up, and listened to a couple people who said i could easily run 265 wide tires on my GTO, and now after purchasing new wheels and tires, i have issues rubbing on my rear fenders...i'm nervous about rolling the fenders themselves, and entered a thread regarding BMR drag bags on the GTO forum, but haven't gotten any confirmation of HOW effective they are at keeping the rear end from sagging into my tires when i dip or cross bumps...i'm estimating i need another 1" of clearance to be totally safe, and i've heard that upgrading springs will help (cause ours tend to sag), but the BMR drag bag only works on OEM springs...please help -- which is going to assist me more, drag bags or new springs? and are there any kind of aftermarket "spring seats" that will raise the existing spring enough to work as well...i really need help fast, cause i don't wanna scar up my tires really bad, so need to do something soon...thanks