Bean07

Hello, new to forum and I'm having problems finding tire height post for a 2007 GT with Steeda ultra springs lowered 1.25 in front 1.5 in rear. 9in front rim 10in rear. I have a turbo nto5 summer perf 275/35/18 25.5in tall up front 295/35/18 26.1in tall rear. I need to get my car off the ground. I got a mmr longblock on the way going to push 900+hp and do not want to bottom out on turbo pipe, and need better grip. Boss block weight to be offset by tubular everything. Nitto 555R has 265/50/18 at 28.4in tall
305/45/18 at 28.7 in tall. Will these tires work without rubbing? Or, what good springs can I get that will not lower my car. Im going to need tires no matter what my rears are shot. If those don't fit what about.
555's at 255/45/18 at 26.9in front and 555R at 305/40/18 at 27.7 in tall rear. Any help would be greatly appreciated even if it's a link to thread. I will be selling the original 3v motor, clutch, 5 speed trans, and driveshaft 1st of January 111000 miles,still in car runs great.