This is just off the top of my head, but with a 9lb pulley on the Powerdyne, I believe I was using a 53 inch belt, 6lb was 53.5. I've since switched to a Vortech. Stock accessory belt should be 90.5 inches
I have a smog pump delete on mine also, and I'm using the 90.5 inch belt. They do list different belts depending on whether you have factory a/c or dealer-installed a/c. Or maybe you have another accessory pulley that is a different size?
My car had underdrive pullies but I just installed stock alt, water pump, and crank pullies. I believe It has factory AC, not sure tho I guess Ill try a 53 inch belt and maybe a 92 1/2 or so