Lenco tower pressure settings

Is there a general rule on how much tower pressure is enough as a starting point in a 3spd blown hemi promod with a heavy 2900 to 3000 lb car with 4.57 gears?
I also would like to get feed back on street driving the same de tuned setup 40lbs or 45lbs or higher on tower pressure. I dont want to slip it much. Thanks.