Changing S/C Pulley 4.8 Joe gibbs

[tndempsey]

I currently have a JGP Reg Cab 4.8 5spd. it has the 3.7" pulley on the S/C I want to change it to a 3.4 or 3.2. I want the most power but not take a risk on blowing the motor. I know I have been told to change to colder plug and re-tune. It currently is putting down 326/349 on a dyno. but that isn't enough. I have been emailing south FL pulley HQ. At first they said go to the 3.2 and now they say go for the 3.4