Help with Rear end gear ratio

I dont know what combination you are going to build but will tell you my combo. It is a 360 W5 engine that runs 10.59 at 127mph at 3000lbs. I am running 31x13.5 tires with a 4.56 gear, shifting at 6200 and crossing the line at 6500. When I put my 28" tires on I would cross the line at 7000 with same shift points. If you already have the tires I would go 4.30 or 4.56 gears. I am planning on trying a 29.5" tire next time I buy some.