Your main concern is towards the middle of the tire. This is wear the tire grows the most. I had about 3" MOL on my 67 SG Cuda at the middle in the front and It never put a mark there. Car ran 5.80's, w/ 16-33-15 slicks.
I was concerned about the front bottom edge of the quarter..right about the middle of the tire. 3" will probably force me to get new tires. I really want to keep the 30 inch tires.