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

But his tires are 2" taller. Hes going to need more gear to rum mid 11s with a 360 and a 30" tire.