id be careful then if your wanting to keep your truck running and dont have the money for a built block. i had a 3.5 upper and 6# lower and madw 18-20 with my 2.6 kb
i had a custom crank pulley made from moto blue. sure it was the size of a grabge can lid, but if youre lookin for the most boost possible keep the upper pulley as big as you can. dunno about the rest of you guys, but i fought pulley wrap and belt slip the whole time i dicked around with the blowers.