Slick size

Ok I have the start of a game plan. I have a built engine, 440+.020, 10.5 compression, 906 heads with work, and a 727 tranny. Lets say conservatively 450 hp. I have the 66 b-cuda to put it in. I have decided to go with the ford 9 because of its price and availability. To shorten it , I need to have my tire and wheel combo picked out.(Dyno straightened me out on that).I know I don't want to run any more than 5500-6000 rpms. I need to figure out what tire size to use. How do you do that? 6", 8", 10" slick? Whats the formula. Thanks.