I'm running #1, and lowered about 0.5" I have no rubbing. However for a stock m I might recommend you go with a third option:
245/265
The reason is with the 275s I don't often break traction on acceleration. Additional grip can actually
slow you down.
After I put in the 3.91 r&p in I'll decide If I stay with 275 rears or bump it down next time I need tires. If you plan on supercharging and/or 4.10s then stick with option #1.