Help with Rear end gear ratio

i run a built 360 in my duster.full steel body and full interior.ran 11.60's with a 3.91 gear.turning around 6500rpm trap.i put a set of 4.30s in the car the the same 28x11.5 tires.the car is turning 7000 trap rpm.i gained 0 time in the 60',1/8,or the 1/4.i am putting the 3.91 back in the car