RE: drag radials
I have the same tires, NT555R's. I'm running 245's also. 255's would probably fit, but i don't thing they would help because as you go wider, it's stressing more to fit on the rim, rounding off the tread surface and giving you less than the actual 255 width touching the ground.
I find that on the street, if i just spin them a little to clean them off, i can get all the traction i need, even with gears and a stall. I've only had them at the track once, and no matter what i did i spun. But that was the track, though, not the tires. Lapeer dragway sucks big time.