You could go as low as 11.50, i did it with a bone stock 427 in a 3500LB 65 Chevelle in the 80's. i have a friend here in La. that runs 6.40's in the 1/8 with a 360 Duster or Demon, don't know which, but she's been running the car for about 25 yrs. I suspect the engine is a little stronger than 400 HP though.
Zip.